fix(oc-file-list-fragment): npe on destroy action mode

Signed-off-by: alperozturk96 <alper_ozturk@proton.me>

Author: alperozturk96

app/src/main/java/com/owncloud/android/ui/fragment/OCFileListFragment.java

@@ -874,16 +874,23 @@ public void onDestroyActionMode(ActionMode mode) {
 
             // show FAB on multi selection mode exit
             if (!mHideFab && !searchFragment) {
-                setFabVisible(mFile.canCreateFileAndFolder());
+                final var file = mFile;
+                if (file != null) {
+                    setFabVisible(file.canCreateFileAndFolder());
+                }
             }
 
-            Activity activity = getActivity();
+            final var activity = getActivity();
             if (activity != null) {
                 viewThemeUtils.platform.resetStatusBar(activity);
             }
 
-            getCommonAdapter().setMultiSelect(false);
-            getCommonAdapter().clearCheckedItems();
+            final var adapter = getCommonAdapter();
+            if (adapter != null) {
+                adapter.setMultiSelect(false);
+                adapter.clearCheckedItems();
+            }
+
             isMultipleFileSelectedForCopyOrMove = false;
         }