Dispose of any mesh, instead of current mesh -- allows for dynamicall…

…y switching mesh type

With this change you can now change in-game (e.g. with voxel-debug):

    game.meshType = 'surfaceMesh'
    game.meshType = 'wireMesh'

and explore new chunks, then the old meshes will be properly cleaned up (vs crashing).

index.js

@@ -486,8 +486,14 @@ Game.prototype.removeFarChunks = function(playerPosition) {
     if (!chunk) return
     var chunkPosition = chunk.position
     if (mesh) {
-      self.scene.remove(mesh[self.meshType])
-      mesh[self.meshType].geometry.dispose()
+      if (mesh.surfaceMesh) {
+        self.scene.remove(mesh.surfaceMesh)
+        mesh.surfaceMesh.geometry.dispose()
+      }
+      if (mesh.wireMesh) {
+        mesh.wireMesh.geometry.dispose()
+        self.scene.remove(mesh.wireMesh)
+      }
       delete mesh.data
       delete mesh.geometry
       delete mesh.meshed