Fix Dropbox auth crash.

Author: Evgenii Kanivets

app/src/main/AndroidManifest.xml

@@ -93,7 +93,7 @@
             android:theme="@style/Theme.Default"
             android:windowSoftInputMode="adjustResize" />
         <activity
-            android:name="com.dropbox.client2.android.AuthActivity"
+            android:name="com.dropbox.core.android.AuthActivity"
             android:configChanges="orientation|keyboard"
             android:launchMode="singleTask"
             android:theme="@android:style/Theme.Translucent.NoTitleBar">

app/src/main/java/com/blogspot/e_kanivets/moneytracker/activity/external/BackupActivity.java

@@ -75,6 +75,8 @@ protected void onResume() {
             try {
                 preferenceController.writeDropboxAccessToken(Auth.getOAuth2Token());
                 btnBackupNow.setEnabled(true);
+                DbxRequestConfig config = new DbxRequestConfig("open_money_tracker");
+                dbClient = new DbxClientV2(config, Auth.getOAuth2Token());
                 fetchBackups();
             } catch (IllegalStateException e) {
                 Timber.e("Error authenticating: %s", e.getMessage());