Make launch activity in your manifest non-mandatory, add in optional override

I am developing an app which I don't want to start an activity from my manifest on run. This makes it so that if you haven't defined such an activity in your manifest, it will simply skip that step rather than crash with an NPE.

I also added :android :launch-activity as an optional override, for example to run a separate
test app which uses your service/sharing intent, etc. or simply a
debugging activity which isn't in your manifest as a launcher.