Defining variables with the same name as private rules leads to undesired behaviour

[CapacitorSet]

Test case:

private rule foo {
    condition: true
}

rule bar {
    condition: foo
}

If you test it with yara testcase.yara /dev/null, it prints a match as expected. However, defining foo as a falsy value prints no matches:

$ yara testcase.yara /dev/null
bar /dev/null
$ yara -d foo="" testcase.yara /dev/null
$ yara -d foo=0 testcase.yara /dev/null

I understand that this is a logically ambiguous case, but I think that the current behaviour is unexpected. I expected the private rule to have precedence over the variable, or an error to be thrown.

Thanks!

[plusvic]

With the latest fix it returns an error.