Npc_HighIndex Bug fixes

[Helladen]

Basically this value is inaccurate, I've tested this and the old code added 1 to the I which it made it 1 off the actual high index. This may have the same effect with the other high indexes, I'm not sure. This also fixes the high index from not resetting, because if there are 0 NPCs on the map then it will not change it.

**Client only!**

Find:
```
    ' Get the npc high Index
    For I = MAX_MAP_NPCS To 1 Step -1
        If MapNpc(I).Num > 0 Then
            Npc_HighIndex = I + 1
            Exit For
        End If
    Next
```
Replace it with:
```
    ' Get the npc high Index
    For I = MAX_MAP_NPCS To 1 Step -1
        If MapNpc(I).Num > 0 Then
            Npc_HighIndex = I
            Exit For
        End If
    Next
```
Above this add:
```
    Npc_HighIndex = 0

```
Below it erase this:
```
    ' Make sure we're not overflowing
    If Npc_HighIndex > MAX_MAP_NPCS Then Npc_HighIndex = MAX_MAP_NPCS
```

[Helladen]

Updated. :P