diff --git a/RELICENSE/xqcool.mq b/RELICENSE/xqcool.mq
new file mode 100644
index 00000000..eb7786d3
--- /dev/null
+++ b/RELICENSE/xqcool.mq
@@ -0,0 +1,15 @@
+# Permission to Relicense under MPLv2 or any other share-alike OSI approved license chosen by the current ZeroMQ BDFL
+
+This is a statement by xqcool
+that grants permission to relicense its copyrights in the libzmq C++
+library (ZeroMQ) under the Mozilla Public License v2 (MPLv2) or any other 
+share-alike Open Source Initiative approved license chosen by the current 
+ZeroMQ BDFL (Benevolent Dictator for Life).
+
+A portion of the commits made by the Github handle "xqcool", with
+commit author "xqcool <xuquan316@live.com>", are copyright of xqcool .
+This document hereby grants the libzmq project team to relicense libzmq, 
+including all past, present and future contributions of the author listed above.
+
+xqcool  
+2020/01/01
diff --git a/src/array.hpp b/src/array.hpp
index a5cd433c..b141a082 100644
--- a/src/array.hpp
+++ b/src/array.hpp
@@ -100,8 +100,9 @@ template <typename T, int ID = 0> class array_t
 
     inline void erase (size_type index_)
     {
-        if (_items.back ())
-            ((item_t *) _items.back ())->set_array_index ((int) index_);
+        if (_items.empty ())
+            return;
+        ((item_t *) _items.back ())->set_array_index ((int) index_);
         _items[index_] = _items.back ();
         _items.pop_back ();
     }