feat(RunModel_Lag): add error if IniStates has a wrong lenght

- Add error IniStates length in RunModel_Lag
- Add corresponding expectation in testhat

Refs #78
4 jobs for 78-states-handling-on-lag-model in 12 minutes and 37 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #140354
build_patched

00:00:30

 
  Regression
passed #140355
regression_patched

00:00:58

 
  Tests
passed #140357
check_as_cran_patched

00:02:13

passed #140356
check_not_cran_patched

00:08:54