Yes it is due to empty stomach only...
If there is no other symptoms with this no need to worry about this problem.
My opinion is you are not suppose to wake your child for feeding while child is sleeping.
Breast feeding is complete food for child at least 6th month, we can not compare breast feeding to any other complementary food
I would advise for bottle feeding:
1.Proper cleaning, washing, boiling and cleaning of bottle.
2.Feeding vessels and rubber teats should be clean with bottle brush and fresh clean water after each feed.
3.Rubber teat should be boiled for few minute and then bottle for at least 10 minutes before use.
4.Strile bottle and nipple should not be contaminated.
5.Rubber nipple periodically changed when it becomes for soft.
6.milk container and wati/spoon should be kept separated and should not used for other purpose.
7.Vitamin supplementation (especially C and D) required for artificial feeding
I wish your child good health
Regards; Dr Sagr Mhatre