fix remaining build errors

src/components/player/PlayerOverlays.tsx

@@ -11,7 +11,7 @@ import SyncPlayPanel from './SyncPlayPanel'
 import type { BaseItemDto } from '../../api/types'
 
 export interface ChapterMarker {
-  StartPositionTicks: number
+  StartPositionTicks?: number | null
   Name?: string | null
   ImageTag?: string | null
 }