Fixed an issue with colliding slugs when modifying a project (#562)

* Fixed an issue with colliding slugs when modifying a project

* Update projects.rs

---------

Co-authored-by: triphora <emma@modrinth.com>

src/routes/projects.rs

@@ -884,7 +884,9 @@ pub async fn project_edit(
                     }
                 }
 
-                {
+                // Make sure the new slug is different from the old one
+                // We are able to unwrap here because the slug is always set
+                if !slug.eq(&project_item.inner.slug.unwrap_or_default()) {
                     let results = sqlx::query!(
                       "
                       SELECT EXISTS(SELECT 1 FROM mods WHERE slug = LOWER($1))