Increase branch coverage: ecma_op_array_get_to_string_at_index (jerryscript-project#9)

Branch coverage:
Before: 5/6
After: 6/6

JerryScript-DCO-1.0-Signed-off-by: Mate Dabis mdabis@inf.u-szeged.hu

Author: matedabis

tests/jerry/array-prototype-join.js

@@ -74,3 +74,16 @@ obj_2[3] = 4;
 obj_2.join = Array.prototype.join;
 
 assert (obj_2.join() === "1,2,3");
+
+/* ES v5.1 15.4.4.5.7.
+   Checking behavior when an element throws error */
+try {
+  var f = function () { throw new TypeError("ooo");};
+  var arr = [0, 1, 2, 3];
+  Object.defineProperty(arr, '0', { 'get' : f });
+  Array.prototype.join.call(arr);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+  assert(e.message == "ooo");
+}