bug#32607: 27.0.50; pop-to-buffer in next-error-no-select

[Juri Linkov]

> Isn't *grep* displayed somewhere when it shows up in the selected
> window and also in some other window?  Maybe the *grep* case is
> special but I still fail to see why.

The special case is in next-error-no-select.  Its purpose is to display
the next-error buffer (the buffer with the location of the next-error),
not to display next-error-last-buffer (the buffer with the list of errors)
because next-error-last-buffer is already displayed.  The user runs
next-error-no-select from the selected window that already displays
next-error-last-buffer, there is no need to try and display the same
buffer again.  This behavior is not even documented.  So pop-to-buffer
is useless here.  But I suspect that maybe it was added for some use cases
to ensure that next-error-last-buffer is displayed.  So at least
we need to make it harmless.  But currently it makes harm with the
reported configuration.  I provided a patch to fix next-error-no-select
to not fail with the legitimate user configuration.