Dont allow blocking local instance (fixes #4241) (#4242)

* Dont allow blocking local instance (fixes #4241)

* use localuserview

crates/api/src/site/block.rs

@@ -19,6 +19,10 @@ pub async fn block_instance(
 ) -> Result<Json<BlockInstanceResponse>, LemmyError> {
   let instance_id = data.instance_id;
   let person_id = local_user_view.person.id;
+  if local_user_view.person.instance_id == instance_id {
+    return Err(LemmyErrorType::CantBlockLocalInstance)?;
+  }
+
   let instance_block_form = InstanceBlockForm {
     person_id,
     instance_id,

crates/utils/src/error.rs

@@ -227,6 +227,7 @@ pub enum LemmyErrorType {
   BanExpirationInPast,
   InvalidUnixTime,
   InvalidBotAction,
+  CantBlockLocalInstance,
   Unknown(String),
 }