Do not allocate memory for zero length strings.

Fixes jerryscript-project#1821.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/parser/js/js-lexer.c

@@ -1197,6 +1197,11 @@ lexer_process_char_literal (parser_context_t *context_p, /**< context */
     parser_raise_error (context_p, PARSER_ERR_LITERAL_LIMIT_REACHED);
   }
 
+  if (length == 0)
+  {
+    has_escape = false;
+  }
+
   literal_p = (lexer_literal_t *) parser_list_append (context_p, &context_p->literal_pool);
   literal_p->prop.length = (uint16_t) length;
   literal_p->type = literal_type;

tests/jerry/regression-test-issue-1833.js

@@ -0,0 +1,16 @@
+// 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.
+
+'\
+'