fix: return None in get_amd_igpu_name when xrandr call fails

If xrandr exits with a non-zero code the except block logged a warning
but execution fell through to the pattern.findall() call, where
xrandr_output was never assigned, causing an immediate NameError crash.
Return None explicitly so callers receive the expected sentinel value.

Author: vjaykrsna

envycontrol.py

@@ -470,6 +470,7 @@ def get_amd_igpu_name():
     except subprocess.CalledProcessError:
         logging.warning(
             "Failed to run the 'xrandr' command.")
+        return None
 
     pattern = re.compile(r'(name:).*(ATI*|AMD*|AMD\/ATI)*')