Improve error message meaning

Change-Id: I085d0f25115e6acd0804b8d547aa58501191b429

plugins/contracts/org.polarsys.chess.contracts.profile/src/org/polarsys/chess/contracts/profile/chesscontract/util/EntityUtil.java

@@ -1820,7 +1820,7 @@ public class EntityUtil {
 		if (initialState != null) {
 			return initialState.getOutgoings();
 		} else {
-			throw new Exception(stateMachine.getName() + " does not have the initial state.");
+			throw new Exception("The state machine of "+((Class) (stateMachine.getOwner())).getName() + " does not have the initial state.");
 		}
 
 	}