MFH: r446250

databases/mongodb: unbreak with clang >= 4.0

Convert ptr > 0 to ptr != 0. As semantics are similar no need for
PORTREVISION bump.

PR: 216213 220857
Submitted by: tobik (based on)
Approved by: maintainer timeout (4 months) + portmgr blanket
Obtained from: upstream (still under APACHE-2.0)
Approved by: ports-secteam blanket