Parse json null as strings or objects
Revert optional json types

This reverts commit 6f399117bfb16a9f96789b6c6ba24add4d8bb171.
This reverts commit d62255a70cd6b59457296445cce81a299e99fc23.
This reverts commit 8be2daf55b3012cfa2d15c4519f6a6798e564618.