Yes, whenever there aren't exactly 2 children, the references / pointers to the remaining children will contain null values (or whatever the equivalent of that is in whichever language it's implemented in).
So 14 will have a null right child, and 1, 4, 7 and 13 will have null left and right children.
I can only speak for a fairly small subset of languages, but you'll definitely need to have some sort of "points to nothing" concept, which these will contain.
The above assumes you have a structure similar to:
node
node left
node right
type value
As an alternative to this representation (although I can't say I've ever seen this used for a binary tree - just presenting the possibility), you could also have an array of children, for example - a size 2 array means both left and right children, a size 1 array means only 1 child - you could perhaps have a flag indicating whether it's a left or right child (or, since it's a BST, you could just compare it to determine which it is), a size 0 array means no children. Note that this array needn't contain any null values.