[bug] MultiDrag Issues on Examples Page

[nguyenank]

Short
This is a series of issues, some more reproducible than others, I found when trying to use MultiDrag, in particular when playing with the MultiDrag example on the examples page.

Issues

• (always occurs) The item is cloned when moving from the left to right list, but not from the right to left. I was unsure if was intentional, but it was definitely not something I expected, so I thought I should bring it up.
• (always occurs) After dragging a set of items, though the green color indicates all of the items are still selected, attempting to drag again shows only the first item is selected and will move.
• (sometimes occurs) Selected items do not appear next to one another after being dragged, but instead are split up with items in between. It does not happen every time, but I have replicated it reasonably well if I select two items and try dragging them as soon as the page loads.
• (occasionally occurs) Multi-selection just will not work with two different responses. Either: items don't turn to green when clicked when another item has already been selected. Or: a newly clicked item changes color to green, but any previously selected items turns back to grey.
• (occasionally occurs) The site crashes completely with a TypeError for undefined, with the crash being proceeded by one or more instances of the error: "select" had indice of "-1", which is probably -1 and doesn't usually happen here.', followed by a CustomEvent with the -1 in the newIndicies. These messages are tied to clicks on the list, which otherwise appear to work fine.

Additional context
Some of these issues (in particular, the crashing error) were actually something I noticed in my personal project, and couldn't figure out the source, so I went to see if I could replicate them on the examples page. Despite these issues, this project has been unbelievably helpful, and I can't thank you enough for creating and continually working on it.

[arturocuya]

@nguyenank Did you find a way to solve any of these issues? The last one is blocking me. Thanks for posting this issue and taking the time to document your experience with the examples. I was going crazy thinking I was the only one with these problems.

[zoomtronic]

i have the "had indice of "-1" problem.. if anyone has the solution .. :)

[microlabig]

similar situation - with multidrag a message appears

"select" had index of "-1", which is probably -1 and doesn't usually happen here.

If you continue to work with multi drag, then the application crashes with an error

I use:

"react-sortablejs": "^6.1.4",
"sortablejs": "^1.15.0"

[ArturoTorresMartinez]

Same error "select" had index of "-1", which is probably -1 and doesn't usually happen here.