Fixes toggling of HTML display mode and header display mode with hotkeys
Fixes toggling of HTML display mode and header display mode with hotkeys

Toggling HTML display mode (hotkey 'x') and header display mode
(hotkey 'h') were broken, because gPrefBranch variable is
undefined with recent Thunderbirds.

Fixes issue #329.

derenio/vimperator-labs,Quicksaver/vimperator-labs,derenio/vimperator-labs,Quicksaver/vimperator-labs