ChakraCore crashes due to null dereference

Both release and debug build of ChakraCore crashes due to the null dereferencing.

PoC:
```
function func_0(f) {
(function (r) {
WScript.Attach(r);
}(f));
}
async function func_1(notAttachCall) {
if (notAttachCall) {
for (let var_0 = 0; var_0 < 1; ++var_0) {
await func_0(func_1);
}
} else {
const var_1 = 0;
}
}
func_1(true);
```
Build Option: None
OS: Ubuntu 18.04.1 LTS
Arch: x86_64