Blender Git Loki

Fix: Wrong variable used to check for metrics files on BLF

Looks like this is has been there since the initial commit
of BLF.

The blf_dir_metrics_search was using the pointer to the
extension of the file and not the full path to check for
metrics files (.afm/.pfm).

Never notice before probably because is not common to use a font
with additional metrics files.