The Bug itself

An empty (but also not empty??The String is not simply an empty string??) string will be displayed if a other text type than

is used.

Recreating the Bug

1. Create a scoreboard objective with

    /scoreboard objectives add ADummy dummy 

2. Give yourself a test-value with

    /scoreboard players set @p ADummy 1337 

3. Summon a creeper with

    /summon creeper ~ ~ ~ {CustomName:"{\"score\":{\"name\":\"@p\",\"objective\":\"ADummy\"}}"} 

In theory this should give the creeper a (displayed) name of "1337". But instead it shows an empty string.
However... If the command

 /data get entity @e[limit=1,type=creeper] 

is run, you can clearly see, that the value of the name, we typed in when we summoned the creeper, is stil in there which suggests there is something wrong with converting scoreboard objectives into plain-name-text.

(This also happens with an item by typing:

 /summon item ~ ~ ~ {Item:{id:"minecraft:torch",Count:1,tag:{display:{Name:"{\"score\":{\"name\":\"@p\",\"objective\":\"ADummy\"}}"}}}} 

)