Need help with the exception when using V-Leaflet add on in my application

Mine is a simple application which uses Vaadin 8 and V-leaflet 2.0.3. I am calling LMap in my UI class just to check if the add on works correctly. I am getting plain screen. Please help on how to fix it.

Note: Apologies for misleading heading as I created this thread to ask about the exception I got during the implementation however I got it rectified and I got another problem.

Here is my pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>org.example</groupId>
<artifactId>MyMap</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>MyMap</name>

<prerequisites>
	<maven>3</maven>
</prerequisites>

<properties>
	<vaadin.version>8.0.0</vaadin.version>
	<vaadin.plugin.version>8.0.0</vaadin.plugin.version>
	<jetty.plugin.version>9.3.9.v20160517</jetty.plugin.version>
	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	<maven.compiler.source>1.8</maven.compiler.source>
	<maven.compiler.target>1.8</maven.compiler.target>
	<!-- If there are no local customisations, this can also be "fetch" or "cdn" -->
	<vaadin.widgetset.mode>local</vaadin.widgetset.mode>
</properties>

<repositories>
	<repository>
		<id>vaadin-addons</id>
		<url>http://maven.vaadin.com/vaadin-addons</url>
	</repository>
</repositories>

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>com.vaadin</groupId>
			<artifactId>vaadin-bom</artifactId>
			<version>${vaadin.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

<dependencies>
	<dependency>
		<groupId>javax.servlet</groupId>
		<artifactId>javax.servlet-api</artifactId>
		<version>3.0.1</version>
		<scope>provided</scope>
	</dependency>
	<dependency>
		<groupId>com.vaadin</groupId>
		<artifactId>vaadin-server</artifactId>
	</dependency>
	<dependency>
		<groupId>com.vaadin</groupId>
		<artifactId>vaadin-push</artifactId>
	</dependency>
	<dependency>
		<groupId>com.vaadin</groupId>
		<artifactId>vaadin-client-compiled</artifactId>
	</dependency>
	<dependency>
		<groupId>com.vaadin</groupId>
		<artifactId>vaadin-themes</artifactId>
	</dependency>
	<!-- https://mvnrepository.com/artifact/org.vaadin.addon/v-leaflet -->
	<dependency>
		<groupId>org.vaadin.addon</groupId>
		<artifactId>v-leaflet</artifactId>

	</dependency>
	<dependency>
		<groupId>org.vaadin.addon</groupId>
		<artifactId>v-leaflet</artifactId>
		<version>2.0.3</version>
	</dependency>

</dependencies>

<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-war-plugin</artifactId>
			<version>3.0.0</version>
			<configuration>
				<failOnMissingWebXml>false</failOnMissingWebXml>
				<!-- Exclude an unnecessary file generated by the GWT compiler. -->
				<packagingExcludes>WEB-INF/classes/VAADIN/widgetsets/WEB-INF/**</packagingExcludes>
			</configuration>
		</plugin>
		<plugin>
			<groupId>com.vaadin</groupId>
			<artifactId>vaadin-maven-plugin</artifactId>
			<version>${vaadin.plugin.version}</version>
			<executions>
				<execution>
					<goals>
						<goal>update-theme</goal>
						<goal>update-widgetset</goal>
						<goal>compile</goal>
						<!-- Comment out compile-theme goal to use on-the-fly theme compilation -->
						<goal>compile-theme</goal>
					</goals>
				</execution>
			</executions>
		</plugin>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-clean-plugin</artifactId>
			<version>3.0.0</version>
			<!-- Clean up also any pre-compiled themes -->
			<configuration>
				<filesets>
					<fileset>
						<directory>src/main/webapp/VAADIN/themes</directory>
						<includes>
							<include>**/styles.css</include>
							<include>**/styles.scss.cache</include>
						</includes>
					</fileset>
				</filesets>
			</configuration>
		</plugin>

		<!-- The Jetty plugin allows us to easily test the development build by
			running jetty:run on the command line. -->
		<plugin>
			<groupId>org.eclipse.jetty</groupId>
			<artifactId>jetty-maven-plugin</artifactId>
			<version>${jetty.plugin.version}</version>
			<configuration>
				<scanIntervalSeconds>2</scanIntervalSeconds>
			</configuration>
		</plugin>
	</plugins>
</build>

<profiles>
	<profile>
		<!-- Vaadin pre-release repositories -->
		<id>vaadin-prerelease</id>
		<activation>
			<activeByDefault>false</activeByDefault>
		</activation>

		<repositories>
			<repository>
				<id>vaadin-prereleases</id>
				<url>http://maven.vaadin.com/vaadin-prereleases</url>
			</repository>
			<repository>
				<id>vaadin-snapshots</id>
				<url>https://oss.sonatype.org/content/repositories/vaadin-snapshots/</url>
				<releases>
					<enabled>false</enabled>
				</releases>
				<snapshots>
					<enabled>true</enabled>
				</snapshots>
			</repository>
		</repositories>
		<pluginRepositories>
			<pluginRepository>
				<id>vaadin-prereleases</id>
				<url>http://maven.vaadin.com/vaadin-prereleases</url>
			</pluginRepository>
			<pluginRepository>
				<id>vaadin-snapshots</id>
				<url>https://oss.sonatype.org/content/repositories/vaadin-snapshots/</url>
				<releases>
					<enabled>false</enabled>
				</releases>
				<snapshots>
					<enabled>true</enabled>
				</snapshots>
			</pluginRepository>
		</pluginRepositories>
	</profile>
</profiles>

</project>


My UI class

package org.example;

import javax.servlet.annotation.WebServlet;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.Button;
import com.vaadin.ui.Label;
import com.vaadin.ui.TextField;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;
import org.vaadin.addon.leaflet.LMap;

/**
 * This UI is the application entry point. A UI may either represent a browser window 
 * (or tab) or some part of a html page where a Vaadin application is embedded.
 * <p>
 * The UI is initialized using {@link #init(VaadinRequest)}. This method is intended to be 
 * overridden to add component to the user interface and initialize non-component functionality.
 */
@Theme("mytheme")
public class MyUI extends UI {
    LMap map;

    @Override
    protected void init(VaadinRequest vaadinRequest) {
        final VerticalLayout layout = new VerticalLayout();
        map = new LMap();
       
        layout.addComponent(map);
        setContent(layout);
    }

    @WebServlet(urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true)
    @VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
    public static class MyUIServlet extends VaadinServlet {
    }
}