Fix RecyclerView crashing

app/src/main/java/com/hippo/ehviewer/ui/scene/FavoritesScene.java

@@ -389,7 +389,6 @@ public class FavoritesScene extends BaseScene implements
             if (1 == mHelper.getShownViewIndex()) {
                 mHasFirstRefresh = false;
             }
-            mHelper = null;
         }
         if (null != mRecyclerView) {
             mRecyclerView.stopScroll();

app/src/main/java/com/hippo/ehviewer/ui/scene/GalleryListScene.java

@@ -518,7 +518,6 @@ public final class GalleryListScene extends BaseScene
             if (1 == mHelper.getShownViewIndex()) {
                 mHasFirstRefresh = false;
             }
-            mHelper = null;
         }
         if (null != mRecyclerView) {
             mRecyclerView.stopScroll();

app/src/main/java/com/hippo/ehviewer/ui/scene/GalleryPreviewsScene.java

@@ -174,7 +174,6 @@ public class GalleryPreviewsScene extends ToolbarScene implements EasyRecyclerVi
             if (1 == mHelper.getShownViewIndex()) {
                 mHasFirstRefresh = false;
             }
-            mHelper = null;
         }
         if (null != mRecyclerView) {
             mRecyclerView.stopScroll();