Fix: a possible crash about lateinit WikipediaApp instance has not en initialized

app/src/main/java/org/wikipedia/WikipediaApp.kt

@@ -40,10 +40,6 @@ import org.wikipedia.util.log.L
 import java.util.UUID
 
 class WikipediaApp : Application() {
-    init {
-        instance = this
-    }
-
     val mainThreadHandler by lazy { Handler(mainLooper) }
     val languageState by lazy { AppLanguageState(this) }
     val appSessionEvent by lazy { AppSessionEvent() }
@@ -137,6 +133,9 @@ class WikipediaApp : Application() {
     override fun onCreate() {
         super.onCreate()
 
+        // Set the instance after the Application is fully initialized.
+        instance = this
+
         WikiSite.setDefaultBaseUrl(Prefs.mediaWikiBaseUrl)
 
         connectionStateMonitor.enable()