blockchain: do not reject chain histories matching only genesis

This is fine if our local chain is so small that it is entirely
contained within the last jump in the peer's short chain history.

src/cryptonote_core/blockchain.cpp

@@ -1828,14 +1828,6 @@ bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qbloc
     return false;
   }
 
-  // if split_height remains 0, we didn't have any but the genesis block in common
-  // which is only fine if the blocks just have the genesis block
-  if(split_height == 0 && qblock_ids.size() > 1)
-  {
-    LOG_ERROR("Ours and foreign blockchain have only genesis block in common... o.O");
-    return false;
-  }
-
   //we start to put block ids INCLUDING last known id, just to make other side be sure
   starter_offset = split_height;
   return true;