Fixed blank tweet resulting in search for @BotName

If the tweet consists of just '@BotName' with no space after the bot name the script would search for @BotName and return a not found error.  The first commit modifies the regex to gobble zero or more spaces after the bot name.  This results in the bot returning the results of a blank search.

The second commit returns the hello message if the tweet is blank instead of a search result.