Fix tline wrapping when out of map bounds

[jtothebell]

Using a bitwise and on the map coordinates in tline makes the sample location wrap around if it should be out of bounds. Pico 8 appears to use sprite 0 if given out of bounds map coordinates in tline, so I've changed this to just use mget. You can see the error on BoneVolt's Sonic game (https://www.lexaloffle.com/bbs/?pid=81589), where before this fix a few garbage pixels are drawn above Sonic's head, but after the fix it looks correct.