* helm-match-plugin.el (helm-mp-highlight-match): Fix when helm buffer is empty.
* helm.el (helm-select-action): Don't send error when no candidates.
* helm.el (helm-get-candidates): Fix invalid-regexp error.
* helm-grep.el: (helm-grep-split-line-regexp): Fix gnus buffer names with ":".
* helm.el (helm-get-candidates): Improve error message.