Fix updating of FIJISettingsCanvas when appending FIUs

I broke it in commit 0c9547b4.

bin/Tk/FIJISettingsViewer.pm

@@ -823,6 +823,7 @@ sub _fiu_cnt {
 sub append_fiu ($) {
     my ($self) = @_;
     $self->_add_fiu_widgets();
+    $self->{'settings_canvas'}->update(); # update Block Diagram
 }
 
 sub remove_fiu ($) {