"Each child must be laid out exactly once."

[BestRazer]

I have a drawer in my flutter application. There I have multiple ListTiles. From the ListTiles, I open PDFs using this plugin. But when I open a pdf, close it and reopen it, it just doesn't show the pdf. Just a grey screen.
Here's how I implemented the ListTiles:
ListTile( title: Text('PDF'), onTap: () { Navigator.pop(context); function(); }, ),
In the console, I get the error
Each child must be laid out exactly once.