[#316] Replace `delete` with assign to `undefined`.
[#316] Replace `delete` with assign to `undefined`.

TukekeSoft/melonJS,gopalindians/melonJS,gopalindians/melonJS,srbala/melonJS,TukekeSoft/melonJS,gopalindians/melonJS,srbala/melonJS,rlugojr/melonJS,srbala/melonJS,rlugojr/melonJS,Smoss/Enoru-eco,rlugojr/melonJS,melonjs/melonJS,MarkoIvanetic/melonJS,Smoss/Enoru-eco,MarkoIvanetic/melonJS,TukekeSoft/melonJS,melonjs/melonJS