Widgetset compilation error - "URI has an authority component"

Flow
1

Getting below error while compiling vaadin add on widgetset

SEVERE: Exception in command execution : java.lang.IllegalArgumentException: URI has an authority component java.lang.IllegalArgumentException: URI has an authority component at java.io.File.(File.java:368)`…,

I am using Vaadin 7.6.1
Add on - ExtFilteringTable

Any form og help appreciated !!