Crash immediately after fetching messages on rotate

Steps

Same as described in #64 (comment 305)

1. Connect to core
2. Find a channel that already has join/part/quit/nick filtering active
3. Disconnect, then wait for new messages to arrive (e.g. monitoring in Quassel desktop)
4. Connect to core with QuasselDroid
5. Open that channel before the channel receives new unfiltered messages

• It may be necessary to wait after connecting to receive filtered messages

6. Rotate the screen

Expected

Chat history fetched after rotate, no crash.

Actual

Chat history fetched after rotate, crash.

v0.4.0-85-g1858b6a8_-_crash_on_rotate_after_message_fetch.txt