Reorder statements logically

deploy.fish

@@ -3,6 +3,12 @@ begin
     set -l dir (status dirname)
     source "$dir/lib/choose-disk.fish"
 
+    set -q WIN11_IMAGE_PATH
+    or begin
+        echo "Please specify the Windows 11 ISO in the `WIN11_IMAGE_PATH` variable."
+        exit 1
+    end
+
     set -l setupLabel "winiso-valhalla"
     set -l buildDir "$(status dirname)/build"
     set -l cacheDir ~/.cache/winiso-valhalla
@@ -11,13 +17,6 @@ begin
     set -l bootPath "/media/boot"
     set -l dataPath "/media/data"
     set -l winpeOverlay (mktemp -d)
-
-    set -q WIN11_IMAGE_PATH
-    or begin
-        echo "Please specify the Windows 11 ISO in the `WIN11_IMAGE_PATH` variable."
-        exit 1
-    end
-
     set -l editionField "Edition ID"
     set -l wimFile "$dataPath/sources/install.wim"