[Bug Report] el-select filterable does not trigger focus properly in the Edge

[GaliMu]

Element UI version

2.4.8

OS/Browsers version

windows 10 / Microsoft EdgeHTML 17.17134

Vue version

2.5.17

Reproduction Link

https://jsfiddle.net/galimu/yfxa7k3h/

Steps to reproduce

1. 点击select输入框，输入框不出现光标但是可以输入文字，这时按 backspace edge浏览器会触发后退功能；
2. 再次点击会显示输入光标但是不能输入文字

What is Expected?

选中select框，出现输入光标，Backspace 触发的是删除功能

What is actually happening?

点击select输入框，输入框不出现光标但是可以输入文字，这时按 backspace edge浏览器会触发后退功能；
再次点击会显示输入光标但是不能输入文字,同时 el-option 会隐藏起来

[element-bot]

Translation of this issue:

Element UI version
2.4.8

OS/Browsers version
Windows 10 / Microsoft EdgeHTML 17.17134

Vue version
2.5.17

Reproduction Link
https://jsfiddle.net/galimu/yfxa7k3h/

Steps to reproduce

1. Click the select input box, the input box does not appear cursor but can enter text, then press the backspace browser will trigger the back-off function;

2. clicking again will display the input cursor but not the text.
   What is Expected?

Check the select box and enter the cursor. Backspace triggers the delete function.
What is actually happening?

Click the select input box, the input box does not appear cursor but can enter text, this time press the backspace ed browser will trigger the function of backoff;
Clicking again will display the input cursor, but not the text, and el-option will hide.

[GaliMu]

#10403
出现的问题和这个差不多