fix: [Ai] issues of input-edit-widget

[LiHua000]

1.reference dialog can not hide normally
2.Optimize the display and hiding of the @ symbol

Log: fix bugs

Bug: https://pms.uniontech.com/bug-view-298457.html
https://pms.uniontech.com/bug-view-298349.html

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在InputEditWidgetPrivate::initEdit函数中，strBeforeCursor变量在循环结束后可能未被赋值，应该在使用前进行检查。
• InputEditWidget::onReferenceBtnClicked函数中，charBeforeCursor变量在cursor.movePosition后可能未被赋值，应该在使用前进行检查。
• InputEditWidget::eventFilter函数中，charSelected变量在cursor.movePosition后可能未被赋值，应该在使用前进行检查。
• InputEditWidget::eventFilter函数中，charSelected变量在cursor.movePosition后可能未被赋值，应该在使用前进行检查。

是否建议立即修改:

• 是

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Kakueeen, LiHua000
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