Fix line anchor char is overriden when overlapping lines

[tuanchauict]

With this test case

{"shapes":[{"type":"L","i":"02-AAeP9cfntWDQPlfHwGZgIcScyLj","idtemp":true,"v":-835964721,"ps":"H|46|21","pe":"V|89|21","jps":["46|21","89|21"],"e":{"su":"S1","ase":true,"asu":"A6","aee":true,"aeu":"A1","du":"1|0|0"},"em":false},{"type":"L","i":"02-AAeP9cfklJ5FYqo9J6KY3la-Ecx","idtemp":true,"v":2000417950,"ps":"H|62|21","pe":"V|89|21","jps":["62|21","89|21"],"e":{"su":"S1","ase":true,"asu":"A6","aee":true,"aeu":"A1","du":"1|0|0"},"em":false}],"connectors":[]}

Before

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After

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