exit SetFn when no argument is given

git-svn-id: https://fhem.svn.sourceforge.net/svnroot/fhem/trunk/fhem@2933 2b470e98-0d58-463d-a4d8-8e2adae1ed80

FHEM/73_PRESENCE.pm

@@ -209,6 +209,8 @@ sub
 PRESENCE_Set($@)
 {
     my ($hash, @a) = @_;
+
+    return "No Argument given" if(!defined($a[1]));
    
     my $usage = ($hash->{MODE} ne "lan-bluetooth" ? "Unknown argument ".$a[1].", choose one of statusRequest " : undef);