MaterialDatePicker - reset initialized flag to false when unload

Author: kevzlou7979

gwt-material/src/main/java/gwt/material/design/client/ui/MaterialDatePicker.java

@@ -138,7 +138,7 @@ public void onUnload() {
         super.onUnload();
 
         dateTemp = getValue();
-        stop();
+        initialize = false;
     }
 
     @Override