Improve white space encode handling on jsonLD exposition endpoint

[rpanfili]

wordlift-plugin/src/classes/jsonld/class-jsonld-endpoint.php

Lines 235 to 239 in 86717a8

	if ( strpos( $meta_value, ' ' ) > 0 ) {
	$meta_values[] = str_replace( ' ', '+', $meta_value );
	} elseif ( strpos( $meta_value, '+' ) > 0 ) {
	$meta_values[] = str_replace( '+', ' ', $meta_value );
	}

Since strpos php function returns boolean false when the provided substring (needle) was not found in the string (haystack), I think this logic is prone to some side-case issues when those chars appears in the first position (which is 0).

To have a better and more reliable and data-agnostic approach I suggest to reword this like:

if (false !== strpos($meta_value, ' ')) {
  [...]
} elseif (false !== strpos($meta_value, '+')) {
  [...]