tel link issue: AMP_Blacklist_Sanitizer class validate_a_node func

AMP_Blacklist_Sanitizer class validate_a_node function fails (tel link is sanitized) for tel hrefs becuase of filter_var specific bug https://php.net/manual/en/filter.filters.validate.php#110411 :
[FAIL] tel:+1-816-555-1212

probably need to add extra exclusion in the function, like:
if ( (false === filter_var( $href, FILTER_VALIDATE_URL ) || ! in_array( $protocol, $valid_protocols ) ) && ($protocol != ‘tel’) ) {