`res$output$maxRelativeOrdinalError` not checked against `NULL`

[Gootjes]

MxModel objects happily let the user navigate to res$output$maxRelativeOrdinalError even though res$output does not exist yet. This way, res$output$maxRelativeOrdinalError can be NULL if model estimations failed (badly), leading to an error at line 100 about comparing against a value that has length 0 (NULL).

https://github.com/cjvanlissa/tidySEM/blob/7ab1d4c4f610da140cd25c72b98fc465b2100a5b/R/syntax-run.R#L100

[cjvanlissa]

Thanks for catching this! Do you have an example of a model that fails in this way, so we can decide how to handle this case?

[Gootjes]

It occurs as the amount of classes go up, and I guess also because I set a time limit on the models. (Sidenote: with a time limit set to 1, it actually takes 3 * 1 minutes to finish because of the current try logic trying harder twice after any kind of failure. I guess there is no logical way to check what kind of error occurred and return immediately on some types of errors?)

## Not run: 
data("empathy")
df <- empathy[1:6][sample.int(nrow(empathy), size = 100*nrow(empathy), replace = T),]
mx_growth_mixture(model = "i =~ 1*ec1 + 1*ec2 + 1*ec3 +1*ec4 +1*ec5 +1*ec6
                           s =~ 0*ec1 + 1*ec2 + 2*ec3 +3*ec4 +4*ec5 +5*ec6
                           ec1 ~~ vec1*ec1
                           ec2 ~~ vec2*ec2
                           ec3 ~~ vec3*ec3
                           ec4 ~~ vec4*ec4
                           ec5 ~~ vec5*ec5
                           ec6 ~~ vec6*ec6
                           i ~~ 0*i
                           s ~~ 0*s
                           i ~~ 0*s",
                  classes = 10,
                  splits = c(10, sample.int(9, size = nrow(df)-1, replace = T)),
                  data = df, run = F) -> res
res <- mxOption(res, key = "Max minutes", value = 1)
m <- run_mx(res)

Running mix10 with 35 parameters
Running mix10 with 35 parameters                                                   
Error in if (res$output$maxRelativeOrdinalError > mxOption(NULL, "mvnRelEps")) { : 
  argument is of length zero
In addition: Warning messages:
1: In runHelper(model, frontendStart, intervals, silent, suppressWarnings,  :
  Time limit of 1 minutes 0 seconds exceeded
2: In runHelper(model, frontendStart, intervals, silent, suppressWarnings,  :
  Time limit of 1 minutes 0 seconds exceeded