SIGN IN SIGN UP

Fix SUBSTR() so that it returns NULL if any argument is NULL.

Ticket #3626. (CVS 6228)

FossilOrigin-Name: 779fce82b7a89b972da488ce8bd35e23ca120c04
D
drh committed
8198d25442cb591cbe2071bfb5aa3c3eb521dc75
Parent: 4e79c59