[TIMOB-25021] Android: Fix deletion of weak global reference

[garymathews]

• Fix deletion of weak global references

TEST CASE

var win = Ti.UI.createWindow({backgroundColor: 'gray', exitOnClose: true});
win.open();

1. Launch application
2. Press back to exit the application
3. Quickly re-launch the application by pressing the application icon (you may want to add a shortcut to your homescreen)
4. This may take a few attempts

JIRA Ticket

[sgtcoolguy]

CR looks good 👍

[ssjsamir]

FR Passed: was able to launch the application and close it and quickly launch it again multiple times without any errors.

Test steps:

• Created a build of the SDK using this PR
• Created a new Titanium project
• Added the following in to the app.js

var win = Ti.UI.createWindow({backgroundColor: 'gray', exitOnClose: true});
win.open();

• Launched the application
• Pressed back to exit the application
• Quickly re-launched the application by pressing the application icon
• Repeated multiple times
• error relating to global issue was no longer shown

Test Environment
Appcelerator Command-Line Interface, version 6.2.3-21
Google Nexus 6P (7.1.1)
Operating System Name: Mac OS X El Capitan
Operating System Version: 10.11.6
Node.js Version: 6.10.1
Appcelerator Studio: 4.9.0.201705302345