Fix Qt6 crash when dragging rows in table views

[Nerixyz]

Description

This PR fixes the crash described in #4563.

I have no clue why the previous code worked in the first place.

• It's quite clear that both from and to are row-indices:
  

  chatterino2/src/common/SignalVectorModel.hpp

  Lines 322 to 323 in 6338d09

  	int from = data->data("chatterino_row_id").toInt();
  	int to = parent.row();

• QAbstractItemModel::index takes a row, column, and (optional) parent (🤓 actually QAbstractTableModel::index is called, but this doesn't do any fancy things).
• to is passed at the second argument - in the position of column 💫

  chatterino2/src/common/SignalVectorModel.hpp

  Line 336 in 6338d09

  this->moveRow(this->index(from, to), from, parent, to);

• to isn't a column-index - this won't end well 🤦‍♀️
• It might happen that the target row index is larger than the amount of columns. In this case, an invalid model-index is returned 🤔
• This invalid index will eventually be used to look up a row in qt-internals 🕵️‍♂️
• This returns a null pointer 🙅‍♂️
• The null pointer will be dereferenced 💥

I changed the column index to 0 which should always be a valid column index. One could also use the column index of parent. But this doesn't really matter since we're moving rows.

Fixes #4563.

[pajlada]

Are you able to reproduce this crash on any non-experimental builds?

[Nerixyz]

Are you able to reproduce this crash on any non-experimental builds?

No. My guess is that somewhere down the line, the invalid index gets sanitized - or sourceParent wasn't used.

[pajlada]

In Qt5, moving rows outputs this warnings:

QAbstractItemModel::endMoveRows:  Invalid index ( -2 , -1 ) in model QAbstractTableModel(0x555fc51b7070)

With your fix, it no longer outputs those warnings 👍

Other than that, I'd just like the changelog entry changed before merging this in

[KararTY]

Very poggers my nammer, thank you Nerixyz.