Fix a crash when the right-side diff doesn't have a header.
Review Request #3802 — Created Jan. 27, 2013 and submitted
Fix a crash when the right-side diff doesn't have a header. There was an error when parsing a diff where there were headers on the left-hand side but not the right-hand side. The solution was found by Ze Lin Xiao at NetApp.
I couldn't devise a repro case, unfortunately. However, it appears to have fixed the problem at NetApp, and logically makes sense. We'll need more real-world testing.