Squashed 'core/' changes from 831eea7..69130d8

69130d8 Update CHANGELOG.md
3fc105e Allow optional 'File' field to be 'null'
a65eb6e Fix exception in toString method

git-subtree-dir: core
git-subtree-split: 69130d875d3f58b356a6d78a506d41b448b102ee
Merge commit '0cdf2dcf9d5d5ea9ff739457e24e5fd75adedd69' into develop