Ypimagepicker: Multiple selections are cleared when albums changed.

[shotat]

Describe the bug

• Multiple selections are cleared when asset collections switched.

To Reproduce
Steps to reproduce the behavior:

1. Go to Gallery（Library）
2. Click on multiple selections button
3. Click on the title view ( Gallery )
4. Click any cells (e.g. Camera Roll) and switch albums.
5. Multiple selections are cleared.

Expected behavior
Selections should remain unchanged.

Environment (please complete the following information):

• Xcode Version 9.3.1
• Swift Version 4.1

Installation Type

• Manual

Additional context
Add any other context about the problem here.

[s4cha]

@shotat Nice catch 👍
Actually it was done on purpose at the time.
Having the selection remain across folders is harder to implement but it's definitely something we want to support in future releases.