Fix use after free when font server connection lost
If there are multiple blocks waiting for the same font, only one of them will have ->freeFont set. The rest will be in a state of FS_DEPENDING.
If the font server dies before the font finishes opening, the block with ->freeFont set will call ->unload_font, invalidating the pfont pointers in the remaining FS_DEPENDING blocks.
Avoid a use after free (and potential crash) by passing conn to fs_cleanup_font instead of dereferencing pfont to find the conn.
Signed-off-by: Peter Harris email@example.com