BeanItemContainer & Grid selection, how to use GetItem() with only Object

I'm having a hard time with this and I'm a beginner so please yell at my bad programming practices and tell me if there's a better way to solve this if possible.

I have a grid. It pulls data from an Access database. (I'm using UCanAccess) I allow the user to filter the entries by Date, then make a selection, and choose to email those entries.

Let's say I run the program. On the page, I choose a date, the Grid will pull the info from that date. I select a few entries, and click the sendToEmailBtn. Everything works.

Now I choose another date, and the grid is refreshed with a different set of entries. Everything displays properly, it pulled the data correctly.

But this time, when I click sendToEmailBtn, I get a nullpointerexception. I'm guessing because the indexID for the grid is now different from the Index of the BeanItemContainer. (since in the code, to change the grid, I simply used removeAllItems) But I'm not sure what to do here? Is there any other way to do this?I tried to just do this

I wanted to try setting the beanHolder = null and resetting up the grid, etc, but I thought there had to be a better way? Unless there isn't? I just wanted to know if there's any other way of using an object to get a bean from BeanItemContainer.

Setting up grid:

[code]BeanContainer<String, Bean> beanHolder = new BeanContainer<String, Bean>(Bean.class);
beanHoldier.setBeanIdProperty("TID");
//Sets up the grid of Beans.
        Grid grid = new Grid (beanHolder);
        grid.setEditorEnabled(true); //Allow changing some parts of the Bean,
                                    //might change later to not allow any changes.
        grid.removeColumn("TID"); //Don't show this column, but it is there.
        grid.setSelectionMode(SelectionMode.MULTI); //Allows to pick multiple entries.

[/code]

This is my date filter button:

dateButton.addClickListener(new ClickListener() {
            private static final long serialVersionUID = 1L;

            @Override
            public void buttonClick(ClickEvent event){
                beanHolder.removeAllItems();
                try {
                    
                    Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
                    Connection conn=DriverManager.getConnection("jdbc:ucanaccess://\\\\server\\folder\\AccessDatabase.mdb");
                     Statement s = conn.createStatement();

                     ResultSet rs = s.executeQuery("SELECT [PLANT], [DEPARTMENT], [Entry-dt], [TID] FROM [Query1] where [RESOURCE] NOT LIKE 'Example*' AND [Entry-dt] = #"+new SimpleDateFormat("MM/dd/yyyy").format(df.getValue())+"#");
                 
                     Bean bean = new Bean();

                     while (rs.next()) {
                         bean.setPlant(rs.getString(1));
                         bean.setDepartment(rs.getString(2));
                         bean.setEntryDate(rs.getString(3).split("\\s")[0].split("-")[1] + rs.getString(3).split("\\s")[0].split("-")[2]+ rs.getString(3).split("\\s")[0].split("-")[0].substring(2));
                         beanHolder.addBean(bean);
                         bean = null;
                         bean = new Bean();
                     }
                     rs.close();
                } catch (ClassNotFoundException | SQLException e) {
                    e.printStackTrace();
                }
                
            }
        });

And this is where the selection error happens (nullpointerexception)

sendToEmailBtn.addClickListener(new ClickListener() {
            private static final long serialVersionUID = 1L;

            @Override
            public void buttonClick(ClickEvent event){
                //*
A lot of email code
               *//
                try{
                //Container to hold failed posted Beans
                    BeanContainer<String, Bean> failureBeans = new BeanContainer<String, Bean>(Bean.class);
                    //Email code cut out


                    //Gets which Time entries were selected by User.
                    MultiSelectionModel selection = (MultiSelectionModel) grid.getSelectionModel();
                    selection.getSelectedRows(); ////////////Error happens here
                    
                    //Cycles through each one and emails
                    for (Object itemId: selection.getSelectedRows()){
                        beanHolder.getItem(itemId).getBean();
                        
                        //tests for failed sent entries
                        if (Body.asText().contains("row 1")){
                            pw.write(beanHolder.getItem(itemId).getBean().toString()+ "\r\n");
                            failureBeans.addBean(beanHolder.getItem(itemId).getBean());
                        }
                            
                    }//End For Loop
                    
                    if (failureBeans.size() >0)
                        UI.getCurrent().addWindow(new BeanErrorWindow(failureBeans));
                    pw.close();
                    webClient.close();
                }catch(FailingHttpStatusCodeException | IOException e){
                    e.printStackTrace();
                }
                Notification.show("Completed.");
            } // Click Event

I changed some of the variable names to try to make the code easier to read.
 

It worked, thank you! I never would have thought of that!