Check the availability of glxinfo before invoking

[rilysh]

glxinfo commands depend on whether you've installed mesa-utils on your system or not, thus it will fail to execute if mesa-utils isn't installed on that system. https://github.com/JhonnyRice/cat-fetch/blob/62d21fd6911d00654d0c9f7c01a166ee2c22d76b/catfetch#L47 Doing like if [ ! glxinfo ]; then ... else ... fi make much sense as if it fails a fallback or even can be prevented from showing device info.