When having DocBlock of function like this:

/**  * Test  *  * @return array  * @throws E   */

Note space after @throws E, then "Squiz.Commenting.FunctionComment" sniff is triggering Uninitialized string offset: 0 notice because in that case comment is text is matched via regexp and is an empty string. Then check for 1st char is a letter is invoked in 205 line and that's triggers a notice.

I think that } else if ($comment === null) { in line 187 in fact should be } else if (empty($comment) === true) { to catch both undefined and empty comments.