Fix unicode_adjust_maxchar(): catch PyUnicode_New() failure
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index d1f2a35..ad0e2e3 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -2084,7 +2084,8 @@
             return;
     }
     copy = PyUnicode_New(len, max_char);
-    _PyUnicode_FastCopyCharacters(copy, 0, unicode, 0, len);
+    if (copy != NULL)
+        _PyUnicode_FastCopyCharacters(copy, 0, unicode, 0, len);
     Py_DECREF(unicode);
     *p_unicode = copy;
 }