Fix warning "suggest braces around empty body in an 'if' statement"

The body of an if statement could become empty if the macro body
is NULL and cause the if to apply to the next line instead.

Signed-off-by: Mike J. Chen <mjchen@google.com>
(cherry picked from bb105972)

Change-Id: Ie4a18920e1fc959910451a70edcff6d7fd16e501