Packages can't have undef names in future parser

FreeBSD sets undef as its dev package list. Spec tests with the future
parser claim this is invalid. This probably should not have worked with
the current parser anyway. This patch adds a conditional so that dev
packages are explicitly installed or not installed if they are needed.

manifests/dev.pp

@@ -4,8 +4,10 @@
   }
   include ::apache::params
   $packages = $::apache::params::dev_packages
-  package { $packages:
-    ensure  => present,
-    require => Package['httpd'],
+  if $packages { # FreeBSD doesn't have dev packages to install
+    package { $packages:
+      ensure  => present,
+      require => Package['httpd'],
+    }
   }
 }