To reproduce:
1. Start lyx 2.2.2, make an empty document
2. insert a table
3. Inside some cell, hit ctrl+space to make a protected space.
(Alternatively, create a horizontal fill, or any of the special
horizontal spaces.)
4. press the mouse somewhere not on on that protected space. drag to
create a selection. release the mouse button when the pointer is on top
of that protected space. The selection may be inside that one cell, span
several cells, or even start outside the table. The far end of the
selection does not matter, only the release point.
This brings up the "Horizontal Space Settings" dialog, and that should
not happen in this case. The dialog is only supposed to happen when
clicking on a protected space (or other horizontal spaces.)
It seems the protected space have to be in a table cell for this to
happen. It does not happen if the protected space is in normal text, or
in a minipage or in a float.
It is not only protected spaces. Put a minipage inside a table cell, and
if selection ends upon it, it will be "clicked" and alternate between
open and closed view. Or if there is a protected space inside, its menu
will pop up.
I guess the same goes for anything that does something when clicked. If
it is inside a table cell and a mouse selection ends on top of it, a
(wrong) click action happens.
Helge Hafting