[Teachers] Fix crashing

services/backend/src/services/teachers.js

@@ -196,6 +196,9 @@ const getTeacherCredits = async (teacherIds, startSemester, endSemester) => {
 
 const yearlyStatistics = async (providers, startSemester, endSemester) => {
   const ids = await getActiveTeachers(providers, startSemester, endSemester)
+  if (!ids || ids.length === 0) {
+    return []
+  }
   const teacherCredits = await getTeacherCredits(ids, startSemester, endSemester)
   return teacherCredits
 }

services/frontend/src/components/Teachers/TeacherSearchTab/index.jsx

@@ -1,7 +1,7 @@
 import { debounce } from 'lodash'
 import { useState, useCallback } from 'react'
 import { Link } from 'react-router-dom'
-import { Message, Icon, Search, Segment, Item } from 'semantic-ui-react'
+import { Message, Icon, Item, Search, Segment } from 'semantic-ui-react'
 
 import { splitByEmptySpace, validateInputLength } from '@/common'
 import { SortableTable } from '@/components/SortableTable'

services/frontend/src/components/Teachers/TeacherStatistics/index.jsx

@@ -142,6 +142,7 @@ export const TeacherStatistics = () => {
           <TeacherStatisticsTable statistics={teacherStats} variant="leaderboard" />
         </Segment>
       )}
+      {!isLoading && !isFetching && teacherData && teacherStats.length === 0 && <Message content="No teachers found" />}
     </div>
   )
 }