do not try to remove whitespace from undefined owserver read return values

git-svn-id: https://svn.fhem.de/fhem/trunk@2538 2b470e98-0d58-463d-a4d8-8e2adae1ed80

fhem/FHEM/10_OWServer.pm

@@ -259,7 +259,7 @@ OWServer_Read($@)
     if($pid == 0) {
       close READER;
       my $ret= OWNet::read($hash->{DEF},$path);
-      $ret =~ s/^\s+//g;
+      $ret =~ s/^\s+//g if(defined($ret));
       Log 5, "OWServer child read $path: $ret";
       delete $hash->{".path"};
       print WRITER $ret;
@@ -274,8 +274,8 @@ OWServer_Read($@)
     return $ret;
   } else {
     my $ret= $hash->{fhem}{owserver}->read($path);
-    $ret =~ s/^\s+//g;
-    return $hash->{fhem}{owserver}->read($path);
+    $ret =~ s/^\s+//g if(defined($ret));
+    return $ret;
   }
 }