fix broken example config file and detect this breakage

IkiWiki/Wrapper.pm

@@ -19,6 +19,9 @@ sub gen_wrapper () { #{{{
 		error("cannot create a wrapper that uses a setup file");
 	}
 	my $wrapper=possibly_foolish_untaint($config{wrapper});
+	if (! defined $wrapper || ! length $wrapper) {
+		error("wrapper filename not specified");
+	}
 	delete $config{wrapper};
 	
 	my @envsave;

doc/ikiwiki.setup

@@ -34,11 +34,9 @@ use IkiWiki::Setup::Standard {
 		},
 		#{
 		#	# The cgi wrapper.
-		#	cgiwrapper => {
-		#		cgi => 1,
-		#		wrapper => "/var/www/wiki/ikiwiki.cgi",
-		#		wrappermode => "06755",
-		#	},
+		#	cgi => 1,
+		#	wrapper => "/var/www/wiki/ikiwiki.cgi",
+		#	wrappermode => "06755",
 		#},
 	],