Partial NBT data matching breaks checking for empty containers

The newly added support for partial matches of NBT data breaks commands that check for empty containers.

Steps to reproduce:

1. Place a container with any item in it, .e.g. with

/setblock ~1 ~ ~ chest 3 replace {Items:[0:{Slot:0b,id:"minecraft:dirt",Damage:0s,Count:1b}]}

2. Check whether the container is empty, e.g. with

/testforblock ~1 ~ ~ chest 3 {Items:[]}

3. The second command returns "Successfully found the block..." despite the container being empty due to the partial matching.