Allow random 0 entries for SaveExistingSpawns

[killerwife]

Just allows randomized entries which have 0 in gameobject table. In future would be best if complete knowledge of what can be in a given spot, but this also helps for now.

[mdX7]

I guess that 0 in id is a CMaNGOS thing? If yes make a comment about it in code, otherwise i might be confused in 10 years xD
I didnt encounter such in tc yet, as we are pooling entire spawns, not just randomize ids

[killerwife]

Yes. In a spawn group you can have 3 levels of randomization, entry (static), random template (simple per spawn random) or spawn group level (spawn group has maxcount of entry 5555 let say). In last case, spawn has to have 0 set if spawn group governs its entry, because there are groups which have a static member entry and rest of spawns in said group are dynamic entry.

[killerwife]

Also fixed.