MarkdownPreviewToggle command doesn't respect mkdp_auto_start

[ArchWand]

Describe the bug With let g:mkdp_auto_start=1, running :MarkdownPreviewToggle opens a second tab instead of closing the first. Note: this appears to be similar to #237

To Reproduce Steps to reproduce the behavior:

1. Put let g:mkdp_auto_start=1 into ~/.config/nvim/init.vim. Save and quit.
2. Open a markdown file. A preview will open.
3. Run :MarkdownPreviewToggle. Another preview will open, despite one already existing.

Expected behavior The toggle command should respect the auto-start variable, and not open a duplicate tab.

Screenshots

Desktop (please complete the following information):

• OS: Ubuntu 22.04

[ArchWand]

My current workaround: disable autostart :\