Fix array length check in lastIndexOf (#3789)

When lastIndexOf is executed the array length can change and in
case of fast arrays the length should be re-checked.

JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.usz@partner.samsung.com

tests/jerry/regression-test-issue-3779.js

@@ -0,0 +1,32 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// 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.
+
+var array = [1, 2, 3];
+var idx_50 = array.lastIndexOf(50, {
+    valueOf: function() {
+        // Trigger removing elements from fast array.
+        array.length = 0;
+    }
+})
+
+assert (idx_50 === -1);
+
+var idx_51 = array.lastIndexOf(51, {
+    valueOf: function() {
+        array.push(51)
+        return 10;
+    }
+})
+
+assert (idx_51 === -1);