Fix changing values from source element parameter editor (only setting the initial value worked).

refs 2950,2562

org.fortiss.af3.allocation.ui/trunk/src/org/fortiss/af3/allocation/ui/editor/treeviewer/.ratings

 ParameterEntryTreeViewerEditingSupport.java 759d5a5462aef5ec2ccd5e0b61b5858d3196145a YELLOW
 ParameterEntryTreeViewerLabelProvider.java c6cd26de2d483a43f013893d0feff158e7cdb1bf YELLOW
-ParameterSourceElementTreeViewerEditingSupport.java 6981413de8dc26e39aa144066ac41fd0181c543f YELLOW
+ParameterSourceElementTreeViewerEditingSupport.java ec180b48e1cb32068c9eab5d60dd4b35fb91899c YELLOW
 ParameterSourceElementTreeViewerLabelProvider.java e2dbecb997ee8e283cd6eb9f91a882a8ec7b75e9 YELLOW
 ParameterTableTreeViewerManager.java d1205500f59668b6b2083295bdade48844bd60f8 YELLOW
 TreeViewerCheckBoxEditingSupport.java ae801bf9e495b983774224444549cfc8c26fee58 YELLOW

org.fortiss.af3.allocation.ui/trunk/src/org/fortiss/af3/allocation/ui/editor/treeviewer/ParameterSourceElementTreeViewerEditingSupport.java

@@ -88,9 +88,9 @@ public class ParameterSourceElementTreeViewerEditingSupport extends EditingSuppo
 					annotationEntry.getSpecificationValue(getAnnotationType(annotationEntry,
 							annotationType));
 
-			// Return empty String instead of null since otherwise the CellEditor cannot be
-			// initialized correctly when editing an empty cell.
-			return value != null ? value : "";
+			// Return String instead object (empty string instead of null) since otherwise the
+			// CellEditor cannot be initialized for editing.
+			return value != null ? value.toString() : "";
 		}
 		return null;
 	}