Fixes a crash when onNewIntent is called before onCreate

app/src/main/java/com/vitorpamplona/amethyst/ui/MainActivity.kt

@@ -158,6 +158,7 @@ class MainActivity : AppCompatActivity() {
     override fun onNewIntent(intent: Intent?) {
         super.onNewIntent(intent)
 
+        if (this::navController.isInitialized) {
             val uri = intent?.data?.toString()
             val startingPage = uriToRoute(uri)
 
@@ -171,6 +172,7 @@ class MainActivity : AppCompatActivity() {
                 }
             }
         }
+    }
 
     private fun isSameRoute(currentRoute: String?, newRoute: String): Boolean {
         if (currentRoute == null) return false