Display message when no matching board was found

ee/app/assets/javascripts/boards/components/boards_selector.vue

@@ -246,6 +246,13 @@ export default {
               class="dropdown-list js-dropdown-list"
               @scroll.passive="throttledSetScrollFade"
             >
+              <li
+                v-show="filteredBoards.length === 0"
+                class="dropdown-item no-pointer-events text-secondary"
+              >
+                {{ s__('IssueBoards|No matching boards found') }}
+              </li>
+
               <li
                 v-for="otherBoard in filteredBoards"
                 :key="otherBoard.id"

locale/gitlab.pot

@@ -4849,6 +4849,9 @@ msgstr ""
 msgid "IssueBoards|Delete board"
 msgstr ""
 
+msgid "IssueBoards|No matching boards found"
+msgstr ""
+
 msgid "IssueBoards|Some of your boards are hidden, activate a license to see them again."
 msgstr ""