Add ! to chomp in result prefix

What does this MR do and why?

Doing result[:prefix]&.chomp || prefix did not work as expected when result[:prefix] was a blank string. Ideally we would want to attach the prefix that is defined before this call to be used when .chomp returns empty string. So by using .chomp!, we get nil when the string is empty, hence we now attach prefix that is defined separately.

I discovered this while working on !132209 (merged) that is still a WIP.

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