Obfuscation of OssLicensesActivity disables using navigation graph to navigate to it [oss-licenses-plugin]

**Describe the bug**
As navigation to OssLicensesActivity using good old startActivity with an Intent works as a charm, using Navigation Graph to achieve the same goal seems counterproductive because of the obfuscation (I suppose).

**To Reproduce**
1. Configure Open Source Notices as in the [docs](https://developers.google.com/android/guides/opensource)
2. Instead of using startActivity, use
`navController.navigate(YourFragment.navigateToOssLicensesActivity())
with properly prepead navigation graph xml

**Expected behavior**
I guess If it wasn't for obfuscation, the activity should have been started.

**Desktop:**
- Gradle version: [3.5.3]
- Android Studio version [3.6.1 (stable)]:
- Plugin name and version:
com.google.android.gms:play-services-oss-licenses:17.0.0
com.google.android.gms:oss-licenses-plugin:0.10.2

**Additional context**
Stacktrace:

` java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xxx.yyy.dev/com.google.android.gms.oss.licenses.OssLicensesActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.android.gms.internal.oss_licenses.zzc.toString()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.android.gms.internal.oss_licenses.zzc.toString()' on a null object reference
at com.google.android.gms.oss.licenses.OssLicensesActivity.onCreate(Unknown Source:11)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:193) 
at android.app.ActivityThread.main(ActivityThread.java:6669) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
E/GmsClient: unable to connect to service: com.google.android.gms.oss.licenses.service.START on com.google.android.gms`