FIX: wrong chain sequence caused by narrow bridge

1.Add filtration for bridge area

github:#3873

Signed-off-by: xun.zhang <xun.zhang@bambulab.com>
Change-Id: I03f7c1ef5bfb86aafdc15065008f0eedfb1a0036

src/libslic3r/PrintObject.cpp

@@ -2629,6 +2629,9 @@ void PrintObject::bridge_over_infill()
                             bridging_area          = closing(bridging_area, flow.scaled_spacing());
                             bridging_area          = intersection(bridging_area, limiting_area);
                             bridging_area          = intersection(bridging_area, total_fill_area);
+                            // BBS: open and close again to filter some narrow parts
+                            bridging_area          = opening(bridging_area, flow.scaled_spacing());
+                            bridging_area          = closing(bridging_area, flow.scaled_spacing());
                             expansion_area         = diff(expansion_area, bridging_area);
 
 #ifdef DEBUG_BRIDGE_OVER_INFILL