fix little bug "[[ ! ]] /usr/bin/screenfetch: line 817: [: 2415.7: integer expression expected"

before this change an error message was displayed on my installation:

[anakin@DeathStar]$ screenfetch 
[ ! ]] /usr/bin/screenfetch: line 817: [: 2415.7: integer expression expected

 [...]

Now seems work well... :)