Crash in BListView::MouseUp()

[jackburton]

The attached application crashes in BListView::MouseUp().

Seems the problem could be the changes in ​https://cgit.haiku-os.org/haiku/commit/?id=6761bf581fd14cac9fd22825fa6baa399263dc83

Specifically, these lines:

-	uint32* buttons = 0;
-	GetMouse(&where, buttons);
+	// if mouse up selection is invalid reselect mouse down selection
+	if (index == -1)
+		index = fTrack->item_index;

where index can be set to an invalid item (0) in certain cases. I encountered the bug myself in Genio. The problem was debugged and tracked down by Andrea Anzani, which also provided the test application.

For reference, here's a link to the Genio issue: ​https://github.com/Genio-The-Haiku-IDE/Genio/issues/228

[waddlesplash]

Fix merged in hrev57476.