Fixed a lacking slash in friends grupo ini file.

A lacking slash was causing the file [AgentID]_fr_groups.ini to be created in the root of data folder (C:\Users\[user]\AppData\Roaming\) instead in Metabolt subfolder and named as METAbolt[AgentID]_fr_groups.ini. Resulting path of the file was like "C:\Users\[user]\AppData\Roaming\METAbolt[AgentID]_fr_groups.ini".