fix: missing problem redirects to homepage

client/pages/Problem.tsx

@@ -1,6 +1,7 @@
+import { route } from 'preact-router'
 import { useContext, useState } from 'preact/hooks'
-import { isAdministrator, Problem as ProblemModel, Solution as SolutionModel } from '../../shared/model'
-import { server } from '../api'
+import { isAdministrator, Solution as SolutionModel } from '../../shared/model'
+import { prependBaseUrl, server } from '../api'
 import { Header } from '../components/Header'
 import { MarkdownEditor } from '../components/MarkdownEditor'
 import { Problem } from '../components/Problem'
@@ -20,9 +21,15 @@ export const ProblemPage = ({ id }: RouteProps) => {
 
     const [source, setSource] = useState('')
 
-    const [{ content }] = useResource<{ content: string }>(`/api/problem/${id}`, {
-        content: '',
-    })
+    const [{ content }] = useResource<{ content?: string }>(
+        `/api/problem/${id}`,
+        {
+            content: '',
+        },
+        () => {
+            route(prependBaseUrl('/'))
+        }
+    )
 
     const [solutions, refreshSolutions, setSolutionHeuristic] = useListResource<SolutionModel>(
         `/api/solutions?problem=${id}`