Merge pull request #7229 from nextcloud/detailCrash

Fix crash on opening details within PreviewText

src/main/java/com/owncloud/android/ui/activity/FileDisplayActivity.java

@@ -138,6 +138,7 @@ import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentTransaction;
 import androidx.localbroadcastmanager.content.LocalBroadcastManager;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 
 import static com.owncloud.android.datamodel.OCFile.PATH_SEPARATOR;
 
@@ -620,7 +621,7 @@ public class FileDisplayActivity extends FileActivity
     OCFileListFragment getListOfFilesFragment() {
         Fragment listOfFiles = getSupportFragmentManager().findFragmentByTag(
             FileDisplayActivity.TAG_LIST_OF_FILES);
-        if (listOfFiles != null) {
+        if (listOfFiles instanceof OCFileListFragment) {
             return (OCFileListFragment) listOfFiles;
         }
         Log_OC.e(TAG, "Access to unexisting list of files fragment!!");
@@ -1037,6 +1038,7 @@ public class FileDisplayActivity extends FileActivity
      *    3. close FAB if open (only if drawer isn't open)
      *    4. navigate up (only if drawer and FAB aren't open)
      */
+    @SuppressFBWarnings("ITC_INHERITANCE_TYPE_CHECKING")
     @Override
     public void onBackPressed() {
         boolean isDrawerOpen = isDrawerOpen();
@@ -1077,6 +1079,8 @@ public class FileDisplayActivity extends FileActivity
                 showSortListGroup(true);
                 cleanSecondFragment();
             }
+        } else if (leftFragment instanceof PreviewTextStringFragment) {
+            createMinFragments(null);
         } else {
             // pop back
             hideSearchView(getCurrentDir());