Utils.pm: better check of time_str2num argument. By Stefan/private mail

git-svn-id: svn://svn.code.sf.net/p/fhem/code/trunk@6660 2b470e98-0d58-463d-a4d8-8e2adae1ed80

fhem/FHEM/99_Utils.pm

@@ -17,7 +17,7 @@ time_str2num($)
 {
   my ($str) = @_;
   my @a;
-  if($str ne "") {
+  if($str) {
     @a = split("[- :]", $str);
     return mktime($a[5],$a[4],$a[3],$a[2],$a[1]-1,$a[0]-1900,0,0,-1);
   } else {