Fix/android load with keys crash on start

[simonljus]

Extending the previous PR #145

When using loadWithKeys instead of capacitor config, the app crashes on start because the params are expected.

ThIs PR will check if the values are defined and skip the initialization logic (assuming the user of the plugin will call loadWithKeys at some point).

Current workaround is catching the error.

// MainActivity.java
public class MainActivity extends BridgeActivity {

    @Override
    public void onStart() {
        try {
            super.onStart();
        } catch (IllegalStateException e) {
            if (isIntercomInitError(e)) {
                Logger.error("MainActivity", "Suppressed Intercom init crash on onStart", e);
            } else {
                throw e;
            }
        }
    }

    private boolean isIntercomInitError(IllegalStateException e) {
        // check if the error comes from Intercom plugin
        return false;
    }
}

What can be improved

For all the other plugin methods, conditionally check if initialized or not and call.reject(REASON)