Fix error message when using TVF without UpdateCB

[svchb]

Fix #767

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 70.72%. Comparing base (cf1a67e) to head (a15eb59).

Files with missing lines	Patch %	Lines
...rc/schemes/fluid/entropically_damped_sph/system.jl	0.00%	1 Missing ⚠️
src/schemes/fluid/transport_velocity.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #807      +/-   ##
==========================================
+ Coverage   70.68%   70.72%   +0.04%     
==========================================
  Files         106      106              
  Lines        6703     6703              
==========================================
+ Hits         4738     4741       +3     
+ Misses       1965     1962       -3     

Flag	Coverage Δ
unit	70.72% <50.00%> (+0.04%)	⬆️

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[LasNikas]

we solved this for the open boundaries as follows:

TrixiParticles.jl/src/schemes/boundary/open_boundary/system.jl

Line 199 in 3eb4996

function reset_callback_flag!(system::OpenBoundarySPHSystem)

It would be nice if we also do so here

[svchb]

It is?

[svchb]

/run-gpu-tests