timeout: avoid panicking for empty string

[353fc443]

Related to #3040

[sylvestre]

Could you please add a test to make sure we don't regress in the future? thanks

[353fc443]

Hi, I'm unable to invoke the error from #3040 using new_ucmd macro

[sylvestre]

#[test]
fn test_command_fail() {
    new_ucmd!()
        .args(&["\"\"", "\"\""])
        .fails()
        .stderr_contains("thread 'main' panicked at");
}

works for me in tests/by-util/test_timeout.rs
(just replace the error message by the new one)

[353fc443]

Unfortunately the error in #3040 is not produced using the above test also @sylvestre .

Tested on Linux and MacOS

Diff < left / right > :
<"timeout: invalid time interval '\"\"': invalid float literal"
>"empty string"

', tests/common/util.rs:326:9

[sylvestre]

ok, i will give it a try :)
thanks

[sylvestre]

I created this:
#3218
(the " were not necessary)