handle various functions no longer dealing with null

web/includes/functions.php

@@ -1959,16 +1959,19 @@ function validNum( $input ) {
 
 // For general strings
 function validStr($input) {
+  if(!$input) return '';
   return strip_tags($input);
 }
 
 // For strings in javascript or tags etc, expected to be in quotes so further quotes escaped rather than converted
 function validJsStr($input) {
+  if(!$input) return '';
   return strip_tags(addslashes($input));
 }
 
 // For general text in pages outside of tags or quotes so quotes converted to entities
 function validHtmlStr($input) {
+  if(!$input) return '';
   return htmlspecialchars($input, ENT_QUOTES);
 }