Core/Player: Add some asserts

Assert PlayerInfo for race/class pair in a few Player functions

(cherry picked from commit 3576a38f6c107d6b17795d84fcb4f87809917299)

src/server/game/Entities/Player/Player.cpp

@@ -23705,6 +23705,7 @@ void Player::ReportedAfkBy(Player* reporter)
 WorldLocation Player::GetStartPosition() const
 {
     PlayerInfo const* info = sObjectMgr->GetPlayerInfo(getRace(), getClass());
+    ASSERT(info);
     uint32 mapId = info->mapId;
     if (getClass() == CLASS_DEATH_KNIGHT && HasSpell(50977))
         mapId = 0;
@@ -24484,6 +24485,7 @@ void Player::LearnCustomSpells()
 
     // learn default race/class spells
     PlayerInfo const* info = sObjectMgr->GetPlayerInfo(getRace(), getClass());
+    ASSERT(info);
     for (PlayerCreateInfoSpells::const_iterator itr = info->customSpells.begin(); itr != info->customSpells.end(); ++itr)
     {
         uint32 tspell = *itr;
@@ -24500,6 +24502,7 @@ void Player::LearnDefaultSkills()
 {
     // learn default race/class skills
     PlayerInfo const* info = sObjectMgr->GetPlayerInfo(getRace(), getClass());
+    ASSERT(info);
     for (PlayerCreateInfoSkills::const_iterator itr = info->skills.begin(); itr != info->skills.end(); ++itr)
     {
         SkillRaceClassInfoEntry const* rcInfo = *itr;