Like the built in nz() function, but substitutes second value if mt() is true.
A variant value
The empty substitution value
nze(Null, "suprise!") => suprise!
nze("", "suprise!") => suprise!
nze("0", "suprise!") => 0 (string)
nze(0, -1) => 0
nze(23, -1) => 23
nze(False, "suprise!") => False