diff --git a/.github/workflows/moodle-plugin-ci.yml b/.github/workflows/moodle-plugin-ci.yml
index edaa4878..37cfd5cd 100644
--- a/.github/workflows/moodle-plugin-ci.yml
+++ b/.github/workflows/moodle-plugin-ci.yml
@@ -8,7 +8,7 @@ jobs:
 
     services:
       postgres:
-        image: postgres:12
+        image: postgres:13
         env:
           POSTGRES_USER: 'postgres'
           POSTGRES_HOST_AUTH_METHOD: 'trust'
@@ -30,35 +30,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        include:
-          - php: '7.4'
-            moodle-branch: 'MOODLE_39_STABLE'
-            database: 'pgsql'
-          - php: '7.4'
-            moodle-branch: 'MOODLE_39_STABLE'
-            database: 'mariadb'
-          - php: '7.4'
-            moodle-branch: 'MOODLE_311_STABLE'
-            database: 'pgsql'
-          - php: '7.4'
-            moodle-branch: 'MOODLE_311_STABLE'
-            database: 'mariadb'
-          - php: '8.0'
-            moodle-branch: 'MOODLE_311_STABLE'
-            database: 'pgsql'
-          - php: '8.0'
-            moodle-branch: 'MOODLE_311_STABLE'
-            database: 'mariadb'
-          - php: '8.0'
-            moodle-branch: 'MOODLE_400_STABLE'
-            database: 'pgsql'
-          - php: '8.0'
-            moodle-branch: 'MOODLE_400_STABLE'
-            database: 'mariadb'
+        php: ['8.1']
+        moodle-branch: ['MOODLE_401_STABLE', 'MOODLE_402_STABLE']
+        database: [pgsql, mariadb]
 
     steps:
       - name: Check out repository code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           path: plugin
 
@@ -66,14 +44,15 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
-          extensions: ${{ matrix.extensions }}
+          extensions:
           ini-values: max_input_vars=5000
-          # none to use phpdbg fallback. Specify pcov (Moodle 3.10 and up) or xdebug to use them instead.
+          # If you are not using code coverage, keep "none". Otherwise, use "pcov" (Moodle 3.10 and up) or "xdebug".
+          # If you try to use code coverage with "none", it will fallback to phpdbg (which has known problems).
           coverage: none
 
       - name: Initialise moodle-plugin-ci
         run: |
-          composer create-project -n --no-dev --prefer-dist moodlehq/moodle-plugin-ci ci ^3
+          composer create-project -n --no-dev --prefer-dist moodlehq/moodle-plugin-ci ci ^4
           echo $(cd ci/bin; pwd) >> $GITHUB_PATH
           echo $(cd ci/vendor/bin; pwd) >> $GITHUB_PATH
           sudo locale-gen en_AU.UTF-8
@@ -85,14 +64,8 @@ jobs:
           cd plugin
           composer install
 
-      - name: Install additional supported plugins (Moodle 3.9-3.11)
-        if: ${{ matrix.moodle-branch == 'MOODLE_39_STABLE' || matrix.moodle-branch == 'MOODLE_310_STABLE' || matrix.moodle-branch == 'MOODLE_311_STABLE' }}
-        run: |
-          moodle-plugin-ci add-plugin --branch MOODLE_34_STABLE catalyst/moodle-mod_facetoface
-          moodle-plugin-ci add-plugin --branch v3.0-stable blindsidenetworks/moodle-mod_bigbluebuttonbn
-
       - name: Install additional supported plugins (Moodle 4.0)
-        if: ${{ matrix.moodle-branch == 'MOODLE_400_STABLE' }}
+        if: ${{ matrix.moodle-branch == 'MOODLE_401_STABLE' || matrix.moodle-branch == 'MOODLE_402_STABLE' }}
         run: |
           moodle-plugin-ci add-plugin --branch MOODLE_400_STABLE catalyst/moodle-mod_facetoface
 
diff --git a/src/transformer/utils/get_string_html_removed.php b/src/transformer/utils/get_string_html_removed.php
index 059d6723..49700834 100644
--- a/src/transformer/utils/get_string_html_removed.php
+++ b/src/transformer/utils/get_string_html_removed.php
@@ -29,7 +29,7 @@
 /**
  * Transformer utility for cleaning HTML from strings.
  *
- * @param string $string The string to clean.
+ * @param null|string $string The string to clean.
  * @return string
  */
 function get_string_html_removed(?string $string) {