CppEditor: fix "Convert to Stack Variable" for empty initializer lists

The "Convert to Stack Variable" quick fix generated invalid code for
the following snippet: QString s = new QString();

Task-number: QTCREATORBUG-14279
Change-Id: I1f5e33d2089bc2d5713eae1e9f4dc5986523112c
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/plugins/cppeditor/cppquickfix_test.cpp

@@ -1559,6 +1559,19 @@ void CppEditorPlugin::test_quickfix_data()
              "        str.clear();\n"
              "}\n");
 
+    QTest::newRow("ConvertFromPointer_withEmptyInitializer")
+        << CppQuickFixFactoryPtr(new ConvertFromAndToPointer)
+        << _("void foo() {\n"
+             "    QString *@str = new QString();\n"
+             "    if (!str->isEmpty())\n"
+             "        str->clear();\n"
+             "}\n")
+        << _("void foo() {\n"
+             "    QString str;\n"
+             "    if (!str.isEmpty())\n"
+             "        str.clear();\n"
+             "}\n");
+
     QTest::newRow("ConvertFromPointer_structWithPointer")
         << CppQuickFixFactoryPtr(new ConvertFromAndToPointer)
         << _("struct Bar{ QString *str; };\n"

src/plugins/cppeditor/cppquickfixes.cpp

@@ -4059,19 +4059,20 @@ private:
 
     void removeNewExpression(ChangeSet &changes, NewExpressionAST *newExprAST) const
     {
-        if (newExprAST->new_initializer) {
+        ExpressionListParenAST *exprlist = newExprAST->new_initializer
+                ? newExprAST->new_initializer->asExpressionListParen()
+                : 0;
+
+        if (exprlist && exprlist->expression_list) {
             // remove 'new' keyword and type before initializer
             changes.remove(m_file->startOf(newExprAST->new_token),
                            m_file->startOf(newExprAST->new_initializer));
 
             // remove parenthesis around initializer
-            if (ExpressionListParenAST *exprlist
-                    = newExprAST->new_initializer->asExpressionListParen()) {
-                int pos = m_file->startOf(exprlist->lparen_token);
-                changes.remove(pos, pos + 1);
-                pos = m_file->startOf(exprlist->rparen_token);
-                changes.remove(pos, pos + 1);
-            }
+            int pos = m_file->startOf(exprlist->lparen_token);
+            changes.remove(pos, pos + 1);
+            pos = m_file->startOf(exprlist->rparen_token);
+            changes.remove(pos, pos + 1);
         } else {
             // remove the whole new expression
             changes.remove(m_file->endOf(m_identifierAST->firstToken()),