gtkselectioninputstream-x11: Do not add unreffed bytes to the chunks queue

This should never happen, but we may exit the loop because of count value
with an unreffed bytes pointer being added back to the chunks queue.

gdk/x11/gdkselectioninputstream-x11.c

@@ -107,7 +107,7 @@ gdk_x11_selection_input_stream_fill_buffer (GdkX11SelectionInputStream *stream,
           memcpy (buffer, g_bytes_get_data (bytes, NULL), size);
       }
 
-    g_bytes_unref (bytes);
+    g_bytes_unref (g_steal_pointer (&bytes));
     result += size;
     if (buffer)
       buffer += size;