Prevent crash

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -67,6 +67,7 @@ import androidx.annotation.Nullable;
 import androidx.appcompat.widget.PopupMenu;
 import androidx.appcompat.widget.SearchView;
 import androidx.constraintlayout.widget.Group;
+import androidx.fragment.app.FragmentActivity;
 import androidx.fragment.app.FragmentTransaction;
 import androidx.lifecycle.Lifecycle;
 import androidx.lifecycle.LifecycleOwner;
@@ -447,22 +448,25 @@ public class FragmentMessages extends FragmentEx {
             selectionTracker.addObserver(new SelectionTracker.SelectionObserver() {
                 @Override
                 public void onSelectionChanged() {
-                    try {
+                    // Workaround AndroidX bug
-                        ViewModelMessages modelMessages = ViewModelProviders.of(getActivity()).get(ViewModelMessages.class);
+                    FragmentActivity activity = getActivity();
-                        LifecycleOwner owner = (viewType == AdapterMessage.ViewType.THREAD ? getViewLifecycleOwner() : getActivity());
+                    if (activity != null) {
+                        ViewModelMessages modelMessages = ViewModelProviders.of(activity).get(ViewModelMessages.class);
+                        LifecycleOwner owner = (viewType == AdapterMessage.ViewType.THREAD ? getViewLifecycleOwner() : activity);
+                        if (selectionTracker.hasSelection())
+                            modelMessages.removeObservers(viewType, owner);
+                        else
+                            modelMessages.observe(viewType, owner, observer);
+                    }
+
                     if (selectionTracker.hasSelection()) {
                         swipeRefresh.setEnabled(false);
-                            modelMessages.removeObservers(viewType, owner);
                         fabMore.show();
                     } else {
                         predicate.clearAccount();
                         fabMore.hide();
-                            modelMessages.observe(viewType, owner, observer);
                         swipeRefresh.setEnabled(pull);
                     }
-                    } catch (IllegalStateException ex) {
-                        Log.w(ex);
-                    }
                 }
             });
         }