Fix a crash in 3D viewer when changing preferences.

It was possible for OnMouseMove to come after ReloadRequest
but before DoRePaint.

Which meant m_3d_render_raytracing->Reload() has't been called yet,
thus the BVH contained invalid data.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/16059

(cherry picked from commit 5cd1a4674f)

3d-viewer/3d_canvas/eda_3d_canvas.cpp

@@ -637,6 +637,9 @@ void EDA_3D_CANVAS::OnMagnify( wxMouseEvent& event )
 
 void EDA_3D_CANVAS::OnMouseMove( wxMouseEvent& event )
 {
+    if( m_3d_render && m_3d_render->IsReloadRequestPending() )
+        return; // Prevents using invalid m_3d_render_raytracing data
+
     if( m_camera_is_moving )
         return;