Catch Standard_Failure before std::exception (OCCT >= 8) (#15826)

Co-authored-by: yw4z <ywsyildiz@gmail.com>

src/libslic3r/CAD/CadDocument.cpp

@@ -2673,10 +2673,10 @@ void CadDocument::apply_feature(TopoDS_Shape& result, bool& have_body,
                 ridge = pipe.Shape();
                 have_ridge = !ridge.IsNull();
             }
+        } catch (const Standard_Failure&) {
+            have_ridge = false; // OCCT failure — on OCCT >= 8 Standard_Failure derives from std::exception, so this handler must come first
         } catch (const std::exception&) {
             have_ridge = false; // fall back to the bare cylinder/bore below
-        } catch (const Standard_Failure&) {
-            have_ridge = false; // OCCT failure (not a std::exception) — must be caught here too
         }
 
         if (f.thread_internal) {

src/slic3r/GUI/CAD/DesignPanel.cpp

@@ -4862,13 +4862,13 @@ void DesignPanel::on_import_mesh()
     try {
         shape = GeometryEngine::mesh_to_brep(mesh.its, MESH_IMPORT_TOLERANCE,
                                              MESH_IMPORT_MERGE_ANGLE_DEG, stats);
-    } catch (const std::exception& e) {
+    } catch (const Standard_Failure& e) {   // on OCCT >= 8 Standard_Failure derives from std::exception — must precede that handler
-        fail(_L("Mesh conversion failed: ") + wxString::FromUTF8(e.what()));
-        return;
-    } catch (const Standard_Failure& e) {   // OCCT throws outside std::exception
         fail(_L("Mesh conversion failed: ") + wxString::FromUTF8(
                  e.GetMessageString() ? e.GetMessageString() : "OCCT error"));
         return;
+    } catch (const std::exception& e) {
+        fail(_L("Mesh conversion failed: ") + wxString::FromUTF8(e.what()));
+        return;
     }
     if (shape.IsNull()) { fail(_L("Mesh conversion produced no geometry")); return; }