java.lang.AssertionError · Tried to resolve the auth promise

Hi,

First off, thanks for putting this plugin together it really saved me a lot of time with our new ReactNative project!

I'm currently seeing a few cases where the `AssertionError` is being thrown due to a `null` Promise in the `AuthenticationCallback`. I haven't been able to isolate the root cause, but it appears to be somewhat timing related with a `cancel()` being called.

### On Authentication Succeeded:

java.lang.AssertionError Tried to resolve the auth promise, but it was already resolved / rejected. This shouldn't happen. 

    FingerprintModule.java:169 io.jari.fingerprint.FingerprintModule$AuthenticationCallback.onAuthenticationSucceeded

    FingerprintManagerCompat.java:301 android.support.v4.hardware.fingerprint.FingerprintManagerCompat$Api23FingerprintManagerCompatImpl$1.onAuthenticationSucceeded

    FingerprintManagerCompatApi23.java:114 android.support.v4.hardware.fingerprint.FingerprintManagerCompatApi23$1.onAuthenticationSucceeded

    FingerprintManager.java:1165 android.hardware.fingerprint.FingerprintManager$MyHandler.sendAuthenticatedSucceeded

    FingerprintManager.java:1096 android.hardware.fingerprint.FingerprintManager$MyHandler.handleMessage

    Handler.java:102 android.os.Handler.dispatchMessage

    Looper.java:154 android.os.Looper.loop

    ActivityThread.java:6688 android.app.ActivityThread.main

    Method.java:-2 java.lang.reflect.Method.invoke

    ZygoteInit.java:1468 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run

    ZygoteInit.java:1358 com.android.internal.os.ZygoteInit.main

### On Authentication Error:

java.lang.AssertionError Tried to reject the auth promise, but it was already resolved / rejected. This shouldn't happen. 

    FingerprintModule.java:147 io.jari.fingerprint.FingerprintModule$AuthenticationCallback.onAuthenticationError

    FingerprintManagerCompat.java:290 android.support.v4.hardware.fingerprint.FingerprintManagerCompat$Api23FingerprintManagerCompatImpl$1.onAuthenticationError

    FingerprintManagerCompatApi23.java:104 android.support.v4.hardware.fingerprint.FingerprintManagerCompatApi23$1.onAuthenticationError

    FingerprintManager.java:1136 android.hardware.fingerprint.FingerprintManager$MyHandler.sendErrorResult

    FingerprintManager.java:1102 android.hardware.fingerprint.FingerprintManager$MyHandler.handleMessage

    Handler.java:102 android.os.Handler.dispatchMessage

    Looper.java:154 android.os.Looper.loop

    ActivityThread.java:6688 android.app.ActivityThread.main

    Method.java:-2 java.lang.reflect.Method.invoke

    ZygoteInit.java:1468 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run

    ZygoteInit.java:1358 com.android.internal.os.ZygoteInit.main

I know the [Android Fingerprint documentation](https://developer.android.com/reference/android/hardware/fingerprint/FingerprintManager.AuthenticationCallback.html#onAuthenticationError(int,java.lang.CharSequence)) specifically mentions that after the `onAuthenticationError` callback executes no other callbacks should be called, but either that isn't true 100% of the time or there may be a currency issue of some kind. Regardless, would you consider downgrading the thrown `AssertionError` to log a warning instead? This would prevent a full application crash in these situations and shouldn't affect the existing JavaScript API since the Promise has already been resolved/rejected.

Start in FingerprintModule.java at the AuthenticationCallback handlers around lines 147 and 169, then trace how cancel() affects the auth Promise. Reproduce the succeeded and error callback cases described in the issue and verify that repeated callbacks no longer crash the application while the existing JavaScript Promise behavior remains unchanged.

Written by the indexing model from the issue text.