updated for version 7.4.379
Problem:    Accessing freed memory after using setqflist(list, 'r'). (Lcd)
Solution:   Reset qf_index.
diff --git a/src/quickfix.c b/src/quickfix.c
index fc3a144..c8954cc 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -2173,6 +2173,7 @@
     }
     vim_free(qi->qf_lists[idx].qf_title);
     qi->qf_lists[idx].qf_title = NULL;
+    qi->qf_lists[idx].qf_index = 0;
 }
 
 /*