* lisp/mh-e/mh-funcs.el (mh-kill-folder), lisp/mh-e/mh-search.el
(mh-index-new-folder), lisp/mh-e/mh-utils.el (mh-prompt-for-folder):
Check for existence of speedbar-buffer rather than
mh-speed-folder-map. The latter can exist if mh-speed has only been
loaded but not displayed.