Crash on rename in diff

The following diff input:

diff --git a/assets/games/welcome/astrobearForWeOnboarding.png b/assets/images/astrobearForWeOnboarding.png
similarity index 100%
rename from assets/games/welcome/astrobearForWeOnboarding.png
rename to assets/images/astrobearForWeOnboarding.png

Result in the module to crash with:

TypeError: Cannot read property 'old_mode' of null
at postProcessDiff (/what-the-diff/lib/parser.js:1886:22