Update prerender-error.md (#14875)

This is to further give more insight on one of the ways to fix prerendering errors especially with dynamic pages.

errors/prerender-error.md

@@ -7,5 +7,5 @@ While prerendering a page an error occurred. This can occur for many reasons fro
 #### Possible Ways to Fix It
 
 - Make sure to move any non-pages out of the `pages` folder
-- Check for any code that assumes a prop is available even when it might not be
+- Check for any code that assumes a prop is available even when it might not be. e.g., have default data for all dynamic pages' props.
 - Check for any out of date modules that you might be relying on