[MC-52617] when checking a tileEntity's Inventory, ignores air.

when using

execute @a ~ ~-1 ~
testforblock ~ ~ ~ dropper 1
{Items:[
0:{id:minecraft:string,Count:1b,Slot:0b},
1:{id:minecraft:string,Count:1b,Slot:2b},
2:{id:minecraft:string,Count:1b,Slot:4b},
3:{id:minecraft:string,Count:1b,Slot:6b},
4:{id:minecraft:string,Count:1b,Slot:8b}
],CustomName:"Crafting Table+"}

(string in a X patern)
it will ignore the top bottom left and right edge slots.
if you put stacks of diamond in those slots it will see them as air or something. and there is no way around it to make it so they will be seen by the system.