MDL-51939 mod_forum: Correct empty groupinfo check

mod/forum/db/upgrade.php

@@ -181,5 +181,13 @@ function xmldb_forum_upgrade($oldversion) {
         upgrade_mod_savepoint(true, 2014051203, 'forum');
     }
 
+    if ($oldversion < 2014051204) {
+        // Groupid = 0 is never valid.
+        $DB->set_field('forum_discussions', 'groupid', -1, array('groupid' => 0));
+
+        // Forum savepoint reached.
+        upgrade_mod_savepoint(true, 2014051204, 'forum');
+    }
+
     return true;
 }

mod/forum/post.php

@@ -840,7 +840,7 @@ if ($fromform = $mform_post->get_data()) {
         // Before we add this we must check that the user will not exceed the blocking threshold.
         forum_check_blocking_threshold($thresholdwarning);
 
-        if (isset($fromform->groupinfo)) {
+        if (!empty($fromform->groupinfo)) {
             // Use the value provided in the dropdown group selection.
             $fromform->groupid = $fromform->groupinfo;
 

mod/forum/version.php

@@ -24,6 +24,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2014051203;       // The current module version (Date: YYYYMMDDXX)
+$plugin->version   = 2014051204;       // The current module version (Date: YYYYMMDDXX)
 $plugin->requires  = 2014050800;       // Requires this Moodle version
 $plugin->component = 'mod_forum';      // Full name of the plugin (used for diagnostics)