fix: Prevent PlayerList::newGame array out-of-bounds and null dereferences

[seer-by-sentry]

This PR addresses a critical crash in Player::init that occurred when loading maps with more player sides than MAX_PLAYER_COUNT.

Root Cause:
In PlayerList::newGame:

1. The first loop iterates through map sides and attempts to initialize players using m_players[m_playerCount++]. If TheSidesList->getNumSides() exceeds MAX_PLAYER_COUNT, m_playerCount goes out of bounds, leading to a garbage pointer being assigned to p. Subsequent call to p->initFromDict(d) then causes an EXCEPTION_ACCESS_VIOLATION_READ.
2. The second loop attempts to find players using findPlayerWithNameKey. For players that were skipped in the first loop (due to exceeding MAX_PLAYER_COUNT or having an empty name key), findPlayerWithNameKey returns nullptr. Subsequent calls to p->setPlayerRelationship() or p->setDefaultTeam() on this nullptr result in a null dereference crash.

Solution:

1. First loop: Added a bounds check if (m_playerCount >= MAX_PLAYER_COUNT) before accessing m_players[m_playerCount++]. If the limit is reached, the side is skipped, and a DEBUG_ASSERTCRASH is triggered to alert developers about oversized maps.
2. Second loop: Added a null check if (!p) after findPlayerWithNameKey to skip processing for players that were not successfully initialized (either due to being skipped in the first loop or being neutral with an empty name key).

Fixes CLIENT-3AP