Yes, This still matters... not fixed.
Also, since it seems that the same crash reports shows whenever the minecraft tried to load an invaild/corrupted json file, your cases may very well be different. If the fix doesn't work, go through your .minecraft folder and find a json file that has 0KB in it and then delete it.
Of cause, by deleting the stats file, your statistics will be gone, and unless you have a backup, there's no way you can recover the statistics data.
Mojang should add an exception which is when it detected an invaild file, the crash report will say where that file is, or even better, automatically generate a new one.
Ok, I just found the corrupted file. In world/stats, if you delete the json file inside, everything will returned to normal.
It seems that for some reason, minecraft voided your stats data. If your situation is the same as mine, you should find a 0KB sized json file in world/stats. Deleting it will cause minecraft to generate a new stats json file, and therefore fixing the null json file issure.
I jsut got the same error with my 1.13 server. The server can load the world, but once a client try to enter the world, the server spilt out this internal server error.
The issure started when the computer hosting the server got a power failure.
(BTW, should i create a seperate issure for this as it happens on a server?)
A video added.