Issue #15876: Fix a refleak in the curses module

The refleak occurred when assigning to window.encoding.

Misc/NEWS

@@ -26,6 +26,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #15876: Fix a refleak in the curses module: window.encoding.
+
 - Issue #15841: The readable(), writable() and seekable() methods of BytesIO
   and StringIO objects now raise ValueError when the object has been closed.
   Patch by Alessandro Moura.

Modules/_cursesmodule.c

@@ -1938,6 +1938,7 @@ PyCursesWindow_set_encoding(PyCursesWindowObject *self, PyObject *value)
     if (ascii == NULL)
         return -1;
     encoding = strdup(PyBytes_AS_STRING(ascii));
+    Py_DECREF(ascii);
     if (encoding == NULL) {
         PyErr_NoMemory();
         return -1;