Fix planepath fill patterns for very small regions. #1463

lib/Slic3r/Fill/PlanePath.pm

@@ -36,7 +36,7 @@ sub fill_surface {
     my $polyline = Slic3r::Polyline->new(
         map [ map {$_*$distance_between_lines} $path->n_to_xy($_) ], @n,
     );
-    return {} if !@$polyline;
+    return {} if @$polyline <= 1;
     
     $self->process_polyline($polyline, $bounding_box);