Fix: compile error due to unnecessary 'mut'

5 jobs for master in 15 minutes and 33 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed clippy #710

00:03:23

passed test #709

00:03:38

 
  Build
passed build #712

00:03:44

passed documentation #711

00:03:45

 
  Testdeploy
passed testdeploy #713

00:01:02