For in-of declaration should only throw error after initialization. (#3541)

This patch fixes the error introduced in #3513.

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

tests/jerry/es2015/forin-header-strict.js

@@ -27,3 +27,35 @@ try {
 } catch (e) {
   assert(e instanceof SyntaxError);
 }
+
+var reached = false;
+
+for (var i in {}) {
+  reached = true;
+}
+assert(!reached);
+
+for (var i of []) {
+  reached = true;
+}
+assert(!reached);
+
+for (let i in {}) {
+  reached = true;
+}
+assert(!reached);
+
+for (let i of []) {
+  reached = true;
+}
+assert(!reached);
+
+for (const i in {}) {
+  reached = true;
+}
+assert(!reached);
+
+for (const i of []) {
+  reached = true;
+}
+assert(!reached);