add_to_log() - fixed a postgres support bug when is set to '', and clarified the logic that decides whether to update the user_students/user_teacher records.

lib/datalib.php

@@ -2383,6 +2383,10 @@ function add_to_log($courseid, $module, $action, $url="", $info="", $cm=0, $user
 
     global $db, $CFG, $USER, $REMOTE_ADDR;
 
+    if ($cm === '') { // postgres won't translate empty string to its default
+        $cm = 0;
+    }
+
     if ($user) {
         $userid = $user;
     } else {
@@ -2401,7 +2405,7 @@ function add_to_log($courseid, $module, $action, $url="", $info="", $cm=0, $user
     if (!$result and ($CFG->debug > 7)) {
         echo "<P>Error: Could not insert a new entry to the Moodle log</P>";  // Don't throw an error
     }
-    if (!$user and isset($USER->id)) {
+    if ( isset($USER) && (empty($user) || $user==$USER->id) ) {
         if ($courseid == 1) {
             update_user_in_db();
         } else if (isstudent($courseid)) {