Free memory after closing the preview and the setting windows

lib/Slic3r/GUI/Plater/ObjectPreviewDialog.pm

@@ -4,7 +4,7 @@ use warnings;
 use utf8;
 
 use Wx qw(:dialog :id :misc :sizer :systemsettings :notebook wxTAB_TRAVERSAL);
-use Wx::Event qw(EVT_BUTTON);
+use Wx::Event qw(EVT_CLOSE);
 use base 'Wx::Dialog';
 
 sub new {
@@ -18,6 +18,12 @@ sub new {
     $self->SetSizer($sizer);
     $self->SetMinSize($self->GetSize);
     
+    # needed to actually free memory
+    EVT_CLOSE($self, sub {
+        $self->EndModal(wxID_OK);
+        $self->Destroy;
+    });
+    
     return $self;
 }
 

lib/Slic3r/GUI/Plater/ObjectSettingsDialog.pm

@@ -29,6 +29,7 @@ sub new {
         $self->{materials}->Closing;
         
         $self->EndModal(wxID_OK);
+        $self->Destroy;
     });
     
     my $sizer = Wx::BoxSizer->new(wxVERTICAL);

lib/Slic3r/GUI/PreviewCanvas.pm

@@ -323,10 +323,6 @@ sub Resize {
     }
 }
  
-sub DESTROY {
-    my $self = shift;
-}
- 
 sub InitGL {
     my $self = shift;