Properly check for a valid selection in minimap.
Changing the dimensions of the map in game setup dialogue recreates the game board. The sector selection is kept. However, the selection might become invalid if the game board shrinks and the selection is not on the board anymore. Adding a new player to the game will then result in checking a sector outside the game board (NULL is returned), so that a method is invoked on a NULL pointer, leading to a crash - see NewGameDlg::slotNewOwner(). This is implemented in Konquest 2.1. BUG: 329163 FIXED-IN: 4.11.5 (cherry picked from commit 238c8f3f)