[Bug tree-optimization/79878] verify_gimple_assign_single: replace error with internal_error

[roland.illig at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79878

--- Comment #1 from Roland Illig <roland.illig at gmx dot de> ---
Two years later, nothing has changed.

As the German translator, I refuse to translate these messages. There is really
nothing a GCC user could take away from a message like "incorrect entry in
label_to_block_map".