"Non-zero property" panic when defining constant property with magnitude 0

[LunarLambda]

The following

example {
    delay const delay 0s
}

causes

The application panicked (crashed).
Message:  Non-zero property
Location: core/src/loader/load.rs:511

In rink 0.8.0.

[LunarLambda]

Offending line is

rink-rs/core/src/loader/load.rs

Line 526 in 1dfa00f

let unit = (&input / &output).expect("Non-zero property").unit;

It makes sense to have this check for regular properties, which are always ratios of some sort, but for constants, having a constant of magnitude 0 (delay, loss, etc...) does make sense, and this panic results because constants are parsed as a ratio of x/1

It would be nice if rink could handle this case, for constants. For now I've just removed the offending properties from substances where it would be magnitude 0.