After expanding tree table, NmCommandBean appears null. How to solve this?

Before rendering the tree table, condition is provided to check the value of Radio button from NmCommandBean. Then tree table is rendered correctly in
collapsed mode as per setting on next page in wizard.  Then I am trying to  expand it by clicking on “+” icon.

After that again focus goes to tree table builder code where NmCommandBean is null. And the expansion goes in infinte loop.

Is there any way to solve this?