Fixed simple missing test that was causing index out of range exceptions

Now will not crash if the map being rendered in cave mode goes up to the height limit.

chunk.py

@@ -531,7 +531,7 @@ class ChunkRenderer(object):
                 ):
                     continue
             elif cave and (
-                    y == 15 and x == 0
+                    y == 15 and x == 0 and z != 127
             ):
                 # If it's on the facing edge, only render if what's
                 # above it is transparent