Bugfix: Cannot use true/false in LTL formulae.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@1623 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/parser/visitor/ConvertForJltl2ba.java

@@ -127,7 +127,7 @@ public class ConvertForJltl2ba extends ASTTraverseModify
 	
 	public void visitPost(ExpressionLiteral e) throws PrismLangException
 	{
-		if (e.getType() instanceof TypeBool) {
+		if (!(e.getType() instanceof TypeBool)) {
 			throw new PrismLangException("Cannot convert expression to jltl2ba form", e);
 		}
 		setFormula(e, new SimpleLTL(e.evaluateBoolean()));