Fix misplaced assert statement causing a lot of warnings

[muffgaga]

I just saw this warning quite often (in the EBRAINS spack build it gets repeated for 162 times ;) ):

/tmp/spack-stage/spack-stage-nest-3.6-uy4os6lc7odhv7bryyp2atuprbdl2xwn/spack-src/nestkernel/connection.h: In member function 'nest::SecondaryEvent* nest::Connection<targetidentifierT>::get_secondary_event()':
/tmp/spack-stage/spack-stage-nest-3.6-uy4os6lc7odhv7bryyp2atuprbdl2xwn/spack-src/nestkernel/connection.h:404:1: warning: no return statement in function returning non-void [-Wreturn-type]
  404 | }
      | ^

Also: I guess even if the assert is ensured to never be removed (contrary to standard NDEBUG behavior) it would be reasonable to clearly state the intention here (an exception might be more user-friendly, but I guess the code was intentionally avoiding an exception) by calling abort?

[terhorstd]

minor change

[gtrensch]

Approved.

[heplesser]

@muffgaga Thanks for this fix! Which compiler and which compiler options do you use? I have not seen this warning before, so our warning settings are apparently not strict enough. Also, even though the limited "Schaffungshöhe" of this PR does not strictly make it necessary, would you send us a contributor agreement (https://nest-simulator.readthedocs.io/en/latest/_downloads/9b65adbdacba6bfed66e68c62af4e308/NEST_Contributor_Agreement.pdf)?

[muffgaga]

@muffgaga Thanks for this fix! Which compiler and which compiler options do you use? I have not seen this warning before, so our warning settings are apparently not strict enough.

It was the EBRAINS Software environment/Collab one — i.e. gcc@10.3.0, and "Release" build was mentioned in the build log (see #2993 for a build issue using the same compiler/software environment). (Maybe NDEBUG was set — I did not investigate deeper → I can, if requested.)

Also, even though the limited "Schaffungshöhe" of this PR does not strictly make it necessary, would you send us a contributor agreement (https://nest-simulator.readthedocs.io/en/latest/_downloads/9b65adbdacba6bfed66e68c62af4e308/NEST_Contributor_Agreement.pdf)?

Yes, will do.

[muffgaga]

NEST_Contributor_Agreement

Yes, will do.

→ sent to @terhorstd (he asked me directly via chat).

[heplesser]

@muffgaga Thanks a lot, will merge now!

[heplesser]

@terhorstd Since you had previously requested changes to this PR, you need to approve it now :).

[terhorstd]

LGTM 👍
Thanks!