Assuming admin db has no objects try In the shell:
> use admin;
> db.runCommand(

);
> db.runCommand(

);
{
"collections" : 0,
"objects" : 0,
"avgObjSize" : NaN,
"dataSize" : 0,
"storageSize" : 0,
"numExtents" : 0,
"indexes" : 0,
"indexSize" : 0,
"fileSize" : 0,
"ok" : 1
}

avgObjSize should be 0 instead of NaN

The binary part of the avgObjSize is:
1,97,118,103,79,98,106,83,105,122,101,0,0,0,0,0,0,0,248,255

0,0,0,0,0,0,248,255 is wrong.