imap/2119: Ambiguous message "Evaluating cache" when header cache is compiled in but switched off

[New Mutt PR <cb@xxxxxxxx>]

>Number:         2119
>Notify-List:    
>Category:       imap
>Synopsis:       Ambiguous message "Evaluating cache" when header cache is 
>compiled in but switched off
>Confidential:   no
>Severity:       minor
>Priority:       low
>Responsible:    mutt-dev
>State:          open
>Keywords:       
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Oct 26 10:20:42 +0200 2005
>Originator:     raorn@xxxxxxxxxxx
>Release:        1.5.11
>Organization:
>Environment:
>Description:
Mutt (IMAP) tries to evaluate empty cache and informs user about it with 
"Evaluating cache" message.  This confuses some users.

This also generates series of useless commands to IMAP server.
>How-To-Repeat:
>Fix:
imap/message.c, imap_read_headers(), #if USE_HCACHE - check
ressult of hc = mutt_hcache_open (HeaderCache, ctx->path); and skip entrie 
#if/#endif block if hc is NULL.  (NOT TESTED).
>Add-To-Audit-Trail:

>Unformatted: