Fix possible crash

app/src/main/java/io/nekohasekai/sfa/ui/main/DashboardFragment.kt

@@ -120,10 +120,12 @@ class DashboardFragment : Fragment(R.layout.fragment_dashboard) {
                     }
                 }
             }.onFailure {
+                withContext(Dispatchers.Main) {
                     activity?.errorDialogBuilder(it)?.show()
                 }
             }
         }
+    }
 
     private fun loopShowDeprecatedNotes(notes: DeprecatedNoteIterator) {
         if (notes.hasNext()) {