PreviewImageActivity: don't try to use virtual folder is type is NONE

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

src/main/java/com/owncloud/android/ui/preview/PreviewImageActivity.java

@@ -60,6 +60,8 @@ import com.owncloud.android.ui.fragment.FileFragment;
 import com.owncloud.android.utils.MimeTypeUtil;
 import com.owncloud.android.utils.theme.ThemeToolbarUtils;
 
+import java.io.Serializable;
+
 import javax.inject.Inject;
 
 import androidx.annotation.NonNull;
@@ -137,8 +139,9 @@ public class PreviewImageActivity extends FileActivity implements
 
     private void initViewPager(User user) {
         // virtual folder
-        if (getIntent().getSerializableExtra(EXTRA_VIRTUAL_TYPE) != null) {
-            VirtualFolderType type = (VirtualFolderType) getIntent().getSerializableExtra(EXTRA_VIRTUAL_TYPE);
+        final Serializable virtualFolderType = getIntent().getSerializableExtra(EXTRA_VIRTUAL_TYPE);
+        if (virtualFolderType != null && virtualFolderType != VirtualFolderType.NONE) {
+            VirtualFolderType type = (VirtualFolderType) virtualFolderType;
 
             mPreviewImagePagerAdapter = new PreviewImagePagerAdapter(getSupportFragmentManager(),
                                                                      type,

src/main/java/com/owncloud/android/ui/preview/PreviewImagePagerAdapter.java

@@ -110,6 +110,9 @@ public class PreviewImagePagerAdapter extends FragmentStatePagerAdapter {
         if (type == null) {
             throw new IllegalArgumentException("NULL parent folder");
         }
+        if(type == VirtualFolderType.NONE){
+            throw new IllegalArgumentException("NONE virtual folder type");
+        }
         if (storageManager == null) {
             throw new IllegalArgumentException("NULL storage manager");
         }