Fix 'Segmentation fault on String.Replace'

Related issue: #747

JerryScript-DCO-1.0-Signed-off-by: László Langó llango.u-szeged@partner.samsung.com

tests/jerry/regression-test-issue-747.js

@@ -0,0 +1,17 @@
+// Copyright 2016 Samsung Electronics Co., Ltd.
+// Copyright 2016 University of Szeged.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+assert (''.replace(/$/g,"a") === "a");
+assert (''.replace(/^/g,"a") === "a");