[js] Get $!cstack from a cursor correctly and prepare for a VMArray being stored there.

Author: pmurias

src/vm/js/RegexCompiler.nqp

@@ -67,8 +67,8 @@ class RegexCompiler {
             self.case($!initial_label),
             self.compile_rx($node),
             self.case($restart_label),
-            "$!cstack = $!cursor[\"\$!cstack\"];",
-            "if ($!cstack instanceof nqp.NQPArray) $!cstack = $!cstack.array;\n",
+            "$!cstack = {self.get_cursor_attr($!cursor, '$!cstack')};",
+            "if ($!cstack && $!cstack.\$\$toArray) $!cstack = $!cstack.\$\$toArray;\n",
             self.case($!fail_label),
             "if ($!bstack.length == 0) \{{self.goto($!done_label)}\}\n",
             "$cstack_top = $!bstack.pop();\n",