01_FHEMWEB.pm: fix warning for global SAVE (Forum #49407)

git-svn-id: svn://svn.code.sf.net/p/fhem/code/trunk@10972 2b470e98-0d58-463d-a4d8-8e2adae1ed80

fhem/FHEM/01_FHEMWEB.pm

@@ -2563,6 +2563,7 @@ FW_Notify($$)
         if($events->[$i] !~ /: /) {
           if($dev->{NAME} eq 'global') { # Forum #47634
             my($type,$args) = split(' ', $events->[$i], 2);
+            $args = "" if(!defined($args)); # global SAVE
             push @data, FW_longpollInfo($h->{fmt}, "$dn-$type", $args, $args);
           }