Fixed in-buffer block overwrites not going to the end of the buffer (#79)

Previously, in-buffer block overwrites would put the new block at the
same place in the buffer order as the old block, which could lead to
incorrect behavior.

Fixes #77.

Author: avdstaaij

gdpc/editor.py

@@ -478,6 +478,7 @@ def _placeSingleBlockGlobalBuffered(self, position: ivec3, block: Block):
         Returns whether placement succeeded."""
         if len(self._buffer) >= self.bufferLimit:
             self.flushBuffer()
+        self._buffer.pop(position, None) # Ensure the new block is added at the *end* of the buffer.
         self._buffer[position] = block
         return True