Update all indentation from tabs to spaces

It seems there were a few stray tabs that used to be there earlier
but since we're now using spaces, we've got rid of all the tabs
permanently.

src/App.svelte

@@ -29,7 +29,7 @@
     }
 
     // Validate email formatting
-    if (!EmailValidator.validate(email)) {
+    if (email && !EmailValidator.validate(email)) {
       errors.push(`"${email}" is not a valid email address`)
     }