build: do not append params if they don't exist.

fractal-matrix-api/src/util.rs

@@ -950,12 +950,15 @@ pub fn build_url(base: &Url, path: &str, params: Vec<(&str, String)>) -> Result<
     let mut url = base.join(path)?;
 
     {
+        // If len was 0 `?` would be appended without being needed.
+        if params.len() >= 1 {
             let mut query = url.query_pairs_mut();
             query.clear();
             for (k, v) in params {
                 query.append_pair(k, &v);
             }
         }
+    }
 
     Ok(url)
 }