Search error results in two displayed messages

Using a 15 character search term and (no wildcard) of "123456789012345" results in an error, which is expected behavior. However two conflicting error messages are displayed:

The following words in your search query were ignored because they are too common words: 123456789012345.
You must specify at least one word to search for. Each word must consist of at least 3 characters and must not contain more than 14 characters excluding wildcards.

If a search was performed, the error message should be "The following words in your search query were ignored because they are too common words:"

If a search was not performed, the error message should be "You must specify at least one word to search for. Each word must consist of at least 3 characters and must not contain more than 14 characters excluding wildcards."

There should only be one error message displayed.

This bug is a fork from discussion of bug #12933 (https://tracker.phpbb.com/browse/PHPBB3-12933)