AbstractFormField: dispose key strokes when field is disposed

KeyStrokes are initialized during the "initField" phase. Consequently,
they must be disposed again during "disposeField".

Change-Id: Ia1fc160cde08a4c59a866079b2fd9b6541648276
Reviewed-on: https://git.eclipse.org/r/111480
Reviewed-by: Beat Schwarzentrub <bsh@bsiag.com>
Tested-by: Beat Schwarzentrub <bsh@bsiag.com>
diff --git a/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractFormField.java b/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractFormField.java
index 2686207..9192f1f 100644
--- a/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractFormField.java
+++ b/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractFormField.java
@@ -994,6 +994,7 @@
   }
 
   protected void disposeFieldInternal() {
+    ActionUtility.disposeActions(getKeyStrokes());
   }
 
   /**