Model errors after sampling if compiled with compile_model_methods = TRUE

[jgabry]

@andrjohns Any idea what's going on here?

Describe the bug

Model errors after sampling if compiled with compile_model_methods = TRUE

To Reproduce

stan_file <- write_stan_file(
"
 parameters {
   real x;
 }
 model {
   x ~ std_normal();
 }
 "
)
mod <- cmdstan_model(stan_file, compile_model_methods = TRUE)
fit <- mod$sample()

This samples but then errors before returning with

Error: Expecting a single string value: [type=NULL; extent=0].
Called from: env$model_ptr(data, seed)

Expected behavior

No error.

Operating system

Mac Big Sur

CmdStanR version number

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