Bug#895056: Dh_Lib.pm: avoid creating empty log of installed files

[Nicolas Boulenguez]

Package: debhelper
Version: 11.1.6
Severity: wishlist
Tags: patch

In Dh_Lib.pm, "sub log_installed_files" starts with:
  return if $dh{NO_ACT};
I suggest
  return if $dh{NO_ACT} or not @patterns;
instead so that the file is only created if it is useful.
(seen with DEB_BUILD_OPTIONS=nodoc dh_installinfo).