update the item count at thumbnails after delete

app/src/main/kotlin/com/simplemobiletools/gallery/adapters/DirectoryAdapter.kt

@@ -294,6 +294,7 @@ class DirectoryAdapter(val activity: SimpleActivity, val dirs: MutableList<Direc
             dirs.removeAll(removeFolders)
             markedItems.clear()
             listener?.tryDeleteFolders(folders)
+            itemCnt = dirs.size
         }
     }
 

app/src/main/kotlin/com/simplemobiletools/gallery/adapters/MediaAdapter.kt

@@ -201,6 +201,7 @@ class MediaAdapter(val activity: SimpleActivity, var media: MutableList<Medium>,
             media.removeAll(removeMedia)
             markedItems.clear()
             listener?.deleteFiles(files)
+            itemCnt = media.size
         }
     }