fix pagination assert (Commit-Boost#450)

Author: ninaiiad

crates/common/src/config/mux.rs

@@ -461,6 +461,7 @@ async fn fetch_ssv_pubkeys_from_public_api(
 
     let mut pubkeys: Vec<BlsPublicKey> = vec![];
     let mut page = 1;
+    let mut expected_total: Option<usize> = None;
 
     loop {
         let route = format!(
@@ -470,21 +471,22 @@ async fn fetch_ssv_pubkeys_from_public_api(
 
         let response = request_ssv_pubkeys_from_public_api(url, http_timeout).await?;
         let fetched = response.validators.len();
+        if expected_total.is_none() && fetched > 0 {
+            expected_total = Some(response.pagination.total);
+        }
         pubkeys.extend(
             response.validators.into_iter().map(|v| v.pubkey).collect::<Vec<BlsPublicKey>>(),
         );
         page += 1;
 
         if fetched < MAX_PER_PAGE {
-            ensure!(
-                pubkeys.len() == response.pagination.total,
-                "expected {} keys, got {}",
-                response.pagination.total,
-                pubkeys.len()
-            );
             break;
         }
     }
 
+    if let Some(expected) = expected_total {
+        ensure!(pubkeys.len() == expected, "expected {expected} keys, got {}", pubkeys.len());
+    }
+
     Ok(pubkeys)
 }