MDL-37339 Administration: Unique custom profile should not be checked…

… if it's empty.

Currently we have two options for custom profile fields 'Unique' and 'Required'
If value s not entered for unique and not required field then we should allow
duplicate empty values. If value is entered then we should check for unique input.
In case field is unique and required then it should be always checked as required
field can't be empty.

user/profile/lib.php

@@ -129,9 +129,19 @@ function edit_validate_field($usernew) {
         global $DB;
 
         $errors = array();
-        /// Check for uniqueness of data if required
-        if ($this->is_unique()) {
-            $value = (is_array($usernew->{$this->inputname}) and isset($usernew->{$this->inputname}['text'])) ? $usernew->{$this->inputname}['text'] : $usernew->{$this->inputname};
+        // Get input value.
+        if (isset($usernew->{$this->inputname})) {
+            if (is_array($usernew->{$this->inputname}) && isset($usernew->{$this->inputname}['text'])) {
+                $value = $usernew->{$this->inputname}['text'];
+            } else {
+                $value = $usernew->{$this->inputname};
+            }
+        } else {
+            $value = '';
+        }
+
+        // Check for uniqueness of data if required.
+        if ($this->is_unique() && (($value !== '') || $this->is_required())) {
             $data = $DB->get_records_sql('
                     SELECT id, userid
                       FROM {user_info_data}