I had the same problem and do not believe it is the “white space”. I tried to delete the white space but nothing resolved.
The solution was simple:
Just replace the file that is the first error:
Warning: Can not modify header information – headers already sent by (output started at / home / agenciac / public_html / functions.php: 2) in / home / agenciac / public_html / wp-includes / pluggable.php on line 881
In most cases the error is in the file of the theme. Then have always booked up the theme. Where there is error only replace the “first larval file error”.
Hugs!
