FIX: fix error path in wipe_tower

jira: none
Change-Id: Ia13ae92c61de0d5a361e7d00ec85ff21a04dfc6c
(cherry picked from commit 8ce8c3ffbb01d29e8a6062d344f3382c7aa886c0)

src/libslic3r/GCode.cpp

@@ -1169,6 +1169,9 @@ static std::vector<Vec2d> get_path_of_change_filament(const Print& print)
                         gcode_out += oss.str();
                     }
                 }
+                old_pos = Vec2f{-1000.1f, -1000.1f};
+                pos     = tcr.tool_change_start_pos;
+                transformed_pos = pos;
             }
         }
         return gcode_out;