Temporarily hidden buffers not shown on highlight/message

1. Disconnect all other Quassel clients from core
2. Connect to core with QuasselDroid
3. Temporarily hide a buffer

• Tested on channel, but may affect queries too

4. Receive a notification from that buffer (highlight, PM, etc)

Expected

Buffer is unhidden in chat list.

Actual

Buffer remains hidden, though notification still shows. Buffer still properly unhides after connecting Quassel desktop/etc.

Additional

This will affect multiple chat lists, not just the currently selected/visible chat list.

Haven't tested permanently-hidden buffers; those should disable notifications anyways.