Fix dir checks

themes/catppuccin/backgrounds.sh

@@ -1,6 +1,6 @@
 BACKGROUNDS_DIR=~/.config/omarchy/backgrounds/catppucin
 
-if [[ -z $BACKGROUNDS_DIR ]]; then
+if [[ ! -d $BACKGROUNDS_DIR ]]; then
   mkdir -p $BACKGROUNDS_DIR
   gum spin --title "Downloading background image..." -- curl -sL -o $BACKGROUNDS_DIR/1-catppuccin.png https://github.com/basecamp/omakub/raw/refs/heads/master/themes/catppuccin/background.png
 fi

themes/tokyo-night/backgrounds.sh

@@ -1,6 +1,6 @@
 BACKGROUNDS_DIR=~/.config/omarchy/backgrounds/tokyo-night
 
-if [[ -z $BACKGROUNDS_DIR ]]; then
+if [[ ! -d $BACKGROUNDS_DIR ]]; then
   mkdir -p $BACKGROUNDS_DIR
   gum spin --title "Downloading background image..." -- curl -sL -o $BACKGROUNDS_DIR/1-Milad-Fakurian-Abstract-Purple-Blue.jpg https://images.unsplash.com/photo-1620207418302-439b387441b0
   gum spin --title "Downloading background image..." -- curl -sL -o $BACKGROUNDS_DIR/2-Pawel-Czerwinski-Abstract-Purple-Blue.jpg https://images.unsplash.com/photo-1651870364199-fc5f9f46ac85