Avoid crash when initializing bugsnag in attachBaseContext

[fractalwrench]

Goal

Avoids a crash when initializing Bugsnag in Application#attachBaseContext(). Previously Bugsnag always attempted to obtain the application context to avoid leaking short-lived activity context. However, at this point in time the application context will return null, resulting in an IllegalArgumentException within the Client constructor.

This changeset fixes this by adding a null check. If the context does return null then it is the base context, and its safe to initialize with as it won't leak memory unlike an Activity.

Testing

Tested manually in an example app as this is not a suitable scenario for mazerunner. Added unit tests to confirm that the original crash does not occur.

[bugsnagbot]

Android notifier sizes

Format	Size impact of Bugsnag (kB)	Size impact of Bugsnag when Minified (kB)
APK	1437.58	1358.81
arm64_v8a	369.25	287.33
armeabi	348.76	266.85
armeabi_v7a	328.3	250.46
x86	406.1	324.18
x86_64	389.72	307.81

Generated by 🚫 Danger

[twometresteve]

LGTM