return variable $new_array in wp-includes/wp-db.php is not initialized

[UnderWordPressure]

Concerns "function get_results($query = null, $output = OBJECT)".

If the query is valid, but the result is empty the "return $new_array"
$new_array is uninitialized.

You can see this, if you enable "error_reporting(E_ALL)".

"$new_array = array();" at the begin of the function will solve the error.

+1 Also, put eyeballs on get_col_info()

(In [13161]) Init array in wpdb:get_results() and get_col_info(). Props UnderWordPressure, miqrogroove, fixes #10607

Referenced: #11799

Finishes the fix, adds minimal improvements.

(In [13671]) Ensure that wpdb::get_results() always returns an array when it should. Fixes #10607 props miqrogroove.

(In [13681]) Check for empty(), not !is_array(), when trying to determine if wpdb::get_results() returned results. See #10607

During the dev chat today, it was brought up that is_null($result) could pose a problem for plugins as a result of [13671].

Checking for is_array() or !is_array() for whether there are or are not results is a similar situation. I made one fix in [13681].

While I doubt we do this elsewhere in core, I wanted to re-open for discussion, as this could definitely break some plugins and I'm not sure there's a good solution;.

Per IRC discussion.