Populate ExtrusionPath::height correctly in case of bridge

lib/Slic3r/Layer/PerimeterGenerator.pm

@@ -368,7 +368,7 @@ sub _traverse_loops {
                     role            => EXTR_ROLE_OVERHANG_PERIMETER,
                     mm3_per_mm      => $self->_mm3_per_mm_overhang,
                     width           => $self->overhang_flow->width,
-                    height          => $self->layer_height,
+                    height          => $self->overhang_flow->height,
                 );
             }