[PATCH] Fix sidebar crash for non-existent mailbox

[Richard Russon]

If you <change-folder> to a non-existent mailbox, there will be no
Context.
---
 sidebar.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sidebar.c b/sidebar.c
index 12971e5..3c2d9c0 100644
--- a/sidebar.c
+++ b/sidebar.c
@@ -886,6 +886,9 @@ void mutt_sb_set_open_buffy (void)
 
   OpnIndex = -1;
 
+  if (!Context)
+    return;
+
   for (entry = 0; entry < EntryCount; entry++)
   {
     if (!mutt_strcmp (Entries[entry]->buffy->realpath, Context->realpath))
-- 
2.7.4