Software version (please complete the following information):
本项目案例10

Describe the bug
在位置足够的情况下，拉取外部新的item 无法放到item末尾

To Reproduce
Steps to reproduce the behavior:
步骤
https://jbaysolutions.github.io/vue-grid-layout/zh/guide/10-drag-from-outside.html
1在这个页面中拉取新的item到第一个位置
2拉长item宽度
3然后重新拉取外部item 就无法放到第一个item后面，此时末尾位置是可以放下的

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
Add any other context about the problem here.