Bug 1455122: Missing block plugin causes upgrade to crash

Change-Id: I607830471cd4ffe2555421b05a2e99eabf74bb06
(cherry picked from commit 34402867)

htdocs/lib/db/upgrade.php

@@ -3967,10 +3967,6 @@ function xmldb_core_upgrade($oldversion=0) {
     if ($oldversion < 2015030403) {
         if ($blocktypes = plugins_installed('blocktype', true)) {
             foreach ($blocktypes as $bt) {
-                // Hack to deal with contactinfo block deletion
-                if ($bt->name == 'contactinfo') {
-                    continue;
-                }
                 install_blocktype_categories_for_plugin(blocktype_single_to_namespaced($bt->name, $bt->artefactplugin));
             }
         }

htdocs/lib/upgrade.php

@@ -1125,7 +1125,10 @@ function get_blocktype_categories() {
 }
 
 function install_blocktype_categories_for_plugin($blocktype) {
-    safe_require('blocktype', $blocktype);
+    if (!safe_require('blocktype', $blocktype, 'lib.php', 'require_once', true)) {
+        // Block has been uninstalled or is missing, so no category data to enter.
+        return;
+    }
     $blocktype = blocktype_namespaced_to_single($blocktype);
     $catsinstalled = get_column('blocktype_category', 'name');
     db_begin();