Explicitly checking whether units is null, undefined, or empty-string to support values of 0 per b/62951440
Explicitly checking whether units is null, undefined, or empty-string to support values of 0 per b/62951440

Change-Id: Ia34771da26ec2b961a0222fca4554dfdbb5c60d4

actions-on-google/actions-on-google-nodejs,actions-on-google/actions-on-google-nodejs,actions-on-google/actions-on-google-nodejs