Apply appearance variable name

Author: form-follows-function

main.py

@@ -102,8 +102,9 @@ def prefsSetStyle(self, sender):
             winAppearance = 'NSAppearanceNameVibrantDark'
         else:
             winAppearance = 'NSAppearanceNameVibrantLight'
-        self.w._window.setAppearance_(NSAppearance.appearanceNamed_(winAppearance))
-        self.prefsWindow._window.setAppearance_(winAppearance)
+        appearance = NSAppearance.appearanceNamed_(winAppearance)
+        self.w._window.setAppearance_(appearance)
+        self.prefsWindow._window.setAppearance_(appearance)
 
 
     def prefsRestoreWarnings(self, sender):