2023-July-16 - 2.6.14417

Fix NPE with loaded save games from past versions. (#11783)

The issue is that old saved games may save references to the GamePlayer on various objects, including pending battles.

Since 2.6 has an invariant that all GamePlayer objects have a non-null getData(), which was not true in 2.5 and earlier, we need to update these after loading the game. In particular, we need to fix up all references to the null player with the instance from the game data.

This was already being done for units and territories via GameData::fixUpNullPlayers(). This adds it also for pending battles.