[Expression.Error] We cannot convert the value null to type Logical.

This part needs to be made conditional

if Row[Charge To Home BU]

This needs a conditional operator say

if Row[Charge To Home BU] <> null 

There's a nifty null coalesce operator ?? now. This allows for handling null checks compactly.

if Row[Charge To Home BU] ?? false then ...

This is a shortcut for

if (if Row[Charge To Home BU] = null then false else Row[Charge To Home BU]) then ...

The operator is documented here (scroll all the way down to the end):
https://docs.microsoft.com/en-us/powerquery-m/m-spec-operators