fix(selectfield): comparison with empty string

Signed-off-by: Thierry Bugier <[email protected]>

Author: btry

inc/fields/selectfield.class.php

@@ -137,6 +137,10 @@ public function getEmptyParameters() {
    }
 
    public function equals($value) {
+      if ($value == '') {
+         // empty string means no selection
+         $value = '0';
+      }
       return $this->value == $value;
    }