Annotations: Enable unsetting enum values

Issue-Ref: 3859
Issue-Url: https://af3-developer.fortiss.org/issues/3859


Signed-off-by: Alexander Diewald <diewald@fortiss.org>

org.fortiss.tooling.base.ui/src/org/fortiss/tooling/base/ui/annotation/editingsupport/.ratings

@@ -7,7 +7,7 @@ ElementEditingSupportBase.java a6360f99ee149276f0fbd299820ebd1c9731ea97 GREEN
 ElementNameEditingSupport.java 0dcaecf4ba5f8ddefa3ccb7d6f4e4506f7f09b26 GREEN
 IMultiValueAnnotationDialog.java b0e0c72c25c5655f8c791bb99b2ed4fd3d0b0c3e GREEN
 IMultiValueAnnotationEditingSupport.java 12e93b20e71e31d30c54e6b9ead8895aaa38454c GREEN
-LabelValueMapping.java 3b7a9c6112cc56595ec99f3b3ea0d469a61ebf1d GREEN
+LabelValueMapping.java 84cb44140f5cede38880b30f446156528592f147 YELLOW
 MultiValueAnnotationDialogBase.java 9d9e6e10e11d1d03a3c5a8c86c3d887aa39e37a6 GREEN
 MultiValueAnnotationEditingSupportBase.java ac228c1a4dec5d7035729585c2dcb9799da6aba9 GREEN
 MultiValueAnnotationSelectionDialog.java eb493c084158bfaf4267d6a1f3dd41bcf0867eef GREEN

org.fortiss.tooling.base.ui/src/org/fortiss/tooling/base/ui/annotation/editingsupport/LabelValueMapping.java

@@ -151,6 +151,10 @@ public class LabelValueMapping {
 			enumValues.add(e.getName());
 			addLabelValuePair(e.getName(), e.getInstance());
 		}
+
+		// Add a "null" entry to allow unsetting the annotation value: The list of enum values does
+		// not contain such "special" literals.
+		addLabelValuePair("", null);
 	}
 
 	/** Returns the set of labels managed by this {@link LabelValueMapping}. */