[TIMOB-28252] Android: Modules built before 9.3.0 will return empty string instead of null

Noticed during the SDK 9.3.0 migration: If you call a module getter and the value is null, thee app now crashes, because a Symbol type is returned instead of a bare null value. This works fine on iOS and used to work fine on Android as well (comparing to 9.2.2.GA). It's easy to replicate: 1. Create a native module and add the following code:

@Kroll.getProperty
public String fcmToken()
{
	return null;
}

2. Add the module to your tiapp.xml with an 9.3.0 SDK included and call the getter:

console.warn(require('ti.test').fcmToken));

3. Notice the error 4. Change the SDK version back to 9.2.2.GA and run the same app again 5. Notice that it's behaving correctly and returning null. I guess it's a regression from some kind of V8 change (see the full 9.2.2 <-- master diff [here](https://github.com/appcelerator/titanium_mobile/compare/9_2_X...9_3_X)). Also see the ti.test module for quick reproduction attached to this ticket. *EDIT*: Found a possible regression candidate [this commit](https://github.com/appcelerator/titanium_mobile/commit/33964f2e8a2d8afa6549e9e99d66612b907b7bff#diff-d5344920be4f1fff291a2472f2046fed4f37659c8de7227cb483aeb4cc167484R220) (as part of TIMOB-27787).