Fix for null pointer exception in case header getFields is null

[abhishekj720]

What changed?
Added a fix for the case when headers's getFields is null.
Causing null pointer in the code.

Why?
Bug fix

How did you test it?
Need to add test for it. will discuss with the team, now adding this to fix bug and unblock customer.

Potential risks
It should be a safe change, as it is returning empty map in case of empty getFields.

Release notes

Documentation Changes

[Groxx]

Yea - makes sense and looks safe to me.

Is this user-controlled / just optional in general so nulls are obviously possible, or is there code somewhere that should be populating this? Now's a good time to go hunting if it's unknown, since this'll basically be hiding the flaw for who knows how long if it actually is a flaw.

(it does seem pretty likely that this is just optional / user controlled though)