Core/Misc: Properly sanitize ReputationSpillover data

Fix an issue added in 024b57bb74 that didn't properly skip ReputationSpillover rows with invalid data.
Fix also a static analysis issue reported by Coverity.

(cherry picked from commit 95b1204798d3ab2a141f81b294b064255c335b8a)

Conflicts:
	src/server/game/Globals/ObjectMgr.cpp

src/server/game/Reputation/ReputationMgr.cpp

@@ -297,7 +297,7 @@ bool ReputationMgr::SetReputation(FactionEntry const* factionEntry, int32 standi
                 {
                     // bonuses are already given, so just modify standing by rate
                     int32 spilloverRep = int32(standing * repTemplate->faction_rate[i]);
-                    SetOneFactionReputation(sFactionStore.LookupEntry(repTemplate->faction[i]), spilloverRep, incremental);
+                    SetOneFactionReputation(sFactionStore.AssertEntry(repTemplate->faction[i]), spilloverRep, incremental);
                 }
             }
         }