Looks like your IEMI has been wiped. I'm not an expert on Sony mobiles, but I believe your IEMI should be saved in /data/nvram/md/NVRAM/NVD_IMEI/MP0B_001. Get Root Explorer and look for the MP0B_001 file. You should be able to find it if you have made a backup of it.
If you don't have a backup, see this video
(watch from the 1min mark) where you can find your IEMI physically-
After finding it, use this chinese tool
to make another MP01B file, copy and paste in the above mentioned directory and set the permissions to rw-rw---- and restart.
I'm sorry if it doesn't work, that's the way one restores IEMIs on MTK handsets, not sure if it's the same method on Sony devices