acciaccatura produces an unwanted time signature

[Ruth Mersmann]

Dear developers,

thank you so much for your work on Lilypond.

I noticed a strange behaviour when using \acciaccatura
It appears a unwanted time signature in the first bar.

This only happens, when there is an other Staff.

I tried my best to check the bug list and to create a minimal example.
I hope, I did it well. Sorry, if not!

How can I fix this problem?

Thanks a lot!
Greetings
Ruth

Minimalbeispiel.ly
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