Hi Pawan,
check out Frisches Neos 4.3 mit Demo Package - Exception im Hauptmenü.
They discuss very similar issues (unfortunately mostly in german).
Basically the say there are problems with typo3fluid and you should try to
- use php7.2 instead of 7.3
- and or downgrade typo3fluid with composer require “typo3fluid/fluid:2.6.0”
For me downgrading to php 7.2 did the trick with Neos 5.0.2.