Bug 220703: return either error or return to avoid crashes and leaks

r/sr=peterv

extensions/transformiix/source/xpath/ExprLexer.cpp

@@ -125,9 +125,6 @@ txExprLexer::parse(const nsASingleFragmentString& aPattern)
   iterator start, end;
   start = aPattern.BeginReading(mPosition);
   aPattern.EndReading(end);
-  if (start == end) {
-    return NS_OK;
-  }
 
   //-- initialize previous token, this will automatically get
   //-- deleted when it goes out of scope

extensions/transformiix/source/xpath/ExprParser.cpp

@@ -179,9 +179,6 @@ txExprParser::createExpr(const nsASingleFragmentString& aExpression,
 {
     NS_ENSURE_ARG_POINTER(aExpr);
     *aExpr = nsnull;
-    if (aExpression.IsEmpty()) {
-        return NS_OK;
-    }
     txExprLexer lexer;
     nsresult rv = lexer.parse(aExpression);
     if (NS_FAILED(rv)) {
@@ -192,6 +189,8 @@ txExprParser::createExpr(const nsASingleFragmentString& aExpression,
     }
     rv = createExpr(lexer, aContext, aExpr);
     if (NS_SUCCEEDED(rv) && lexer.peek()->mType != Token::END) {
+        delete *aExpr;
+        *aExpr = nsnull;
         rv = NS_ERROR_XPATH_BINARY_EXPECTED;
     }
     if (NS_FAILED(rv)) {