Merge pull request #1013 from Yakindu/issue_726

#726: Clearing cell editor text when new value is null.

plugins/org.yakindu.sct.simulation.ui/src/org/yakindu/sct/simulation/ui/view/ExecutionContextLabelProvider.java

@@ -58,6 +58,8 @@ public class ExecutionContextLabelProvider extends StyledCellLabelProvider {
 				} else {
 					cell.setText(value.toString());
 				}
+			} else {
+				cell.setText("");
 			}
 		}
 	}