koreader/koreader — pull request #487 by thotypous (2014-01-22 12:03:56+00:00)
Title: Cleanup link_states and fix a rare highlight bug

Found how to reproduce the bug which was unsolved in #485: @chrox was right, there was some cleanup missing. Also fix a rare highlight bug which got me a crash yesterday:
```
./luajit: ./frontend/ui/reader/readerhighlight.lua:300: attempt to index field 'hold_pos' (a nil value)
stack traceback:
./frontend/ui/reader/readerhighlight.lua:300: in function 'lookup'
./frontend/ui/reader/readerhighlight.lua:320: in function 'handleEvent'
./frontend/ui/widget/container/widgetcontainer.lua:63: in function 'propagateEvent'
./frontend/ui/widget/container/widgetcontainer.lua:75: in function 'handleEvent'
./frontend/ui/uimanager.lua:119: in function 'sendEvent'
./frontend/ui/uimanager.lua:307: in function 'run'
./reader.lua:196: in main chunk
[C]: in function 'dofile'
./koreader-base:37: in main chunk
[C]: at 0x0000c604
```