check for account in onResume mixin

Signed-off-by: Ole Bittner <dev@oleb.it>

app/src/main/java/com/nextcloud/client/mixins/SessionMixin.kt

@@ -133,4 +133,11 @@ class SessionMixin constructor(
         val account = accountManager.currentAccount
         setAccount(account)
     }
+
+    override fun onResume() {
+        super.onResume()
+        if (currentAccount == null) {
+            swapToDefaultAccount()
+        }
+    }
 }

app/src/main/java/com/owncloud/android/ui/activity/BaseActivity.java

@@ -89,7 +89,9 @@ public abstract class BaseActivity extends AppCompatActivity implements Injectab
     @Override
     protected void onResume() {
         super.onResume();
-        mixinRegistry.onResume();
+        if (enableAccountHandling) {
+            mixinRegistry.onResume();
+        }
         paused = false;
 
         if (themeChangePending) {