Bug fix in simplification of implication (affects explicit engine) (from Philipp Chrszon).

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@9374 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/parser/visitor/Simplify.java

@@ -50,7 +50,7 @@ public class Simplify extends ASTTraverseModify
 			if (Expression.isFalse(e.getOperand1()) || Expression.isTrue(e.getOperand2()))
 				return Expression.True();
 			if (Expression.isFalse(e.getOperand2()))
-				return e.getOperand1();
+				return Expression.Not(e.getOperand1());
 			if (Expression.isTrue(e.getOperand1()))
 				return e.getOperand2();
 			break;