getPossibleValues should return null to avoid a drop down menu in some of the rodin editors

de.prob.ui/src/de/prob/ui/pragmas/InferredUnitPragmaAttribute.java

@@ -39,7 +39,7 @@ public class InferredUnitPragmaAttribute implements IAttributeManipulation {
 	@Override
 	public String[] getPossibleValues(IRodinElement element,
 			IProgressMonitor monitor) {
-		return new String[] { "", "a", "b", "c" };
+		return null;
 	}
 
 	@Override

de.prob.ui/src/de/prob/ui/pragmas/UnitPragmaAttribute.java

@@ -38,7 +38,7 @@ public class UnitPragmaAttribute implements IAttributeManipulation {
 	@Override
 	public String[] getPossibleValues(IRodinElement element,
 			IProgressMonitor monitor) {
-		return new String[] { "", "a", "b", "c" };
+		return null;
 	}
 
 	@Override