obs-filter: NVIDIA Effects, log version only if lib is found

[pkviet]

Description

This puts the version logging behind a condition of having found a lib.

Motivation and Context

A user reported in beta channel that his log reported an nvidia fx version 0.0.0.0. This should not be logged because this means the nvidia sdk is not installed.

How Has This Been Tested?

If no version of the sdk is returned, there's no log anymore.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.