BHV-16979: Adjust buffer +1 when IntegerPicker has negative min and set digits size.

When min is -100 and digits is 5, IntegerPicker can show "-00100" which is having length of 6.
So, add buffer length by 1 on this case.

DCO-1.1-Signed-Off-By: Kunmyon Choi kunmyon.choi@lge.com