diff -ur mutt-1.7.0-orig/imap/imap.c mutt-1.7.0/imap/imap.c

--- mutt-1.7.0-orig/imap/imap.c	2016-08-20 11:06:26.266272415 +0100

+++ mutt-1.7.0/imap/imap.c	2016-08-20 11:07:42.874509429 +0100

@@ -1143,7 +1143,7 @@

   if (!idata->ctx)

     return -1;

-  if (!mutt_bit_isset (idata->ctx->rights, right))

+  if (!idata->ctx || !mutt_bit_isset (idata->ctx->rights, right))

     return 0;

   if (right == MUTT_ACL_WRITE && !imap_has_flag (idata->flags, name))