#2 Install omod confusion

[niaht]

There is a minor bug in the code that handles installing an omod from the explorer context menu.

To Reproduce:

1. Close OBMM.
2. Remove omod from the 'mods' folder manually. (move it somewhere else)
3. 'Open' the same omod from outside the 'mods' folder.
4. OBMM will report that the mod appears to already be installed.
5. 'opening' the omod again after this will perform as expected, until steps are repeated.