Update Units.php

[yarscript]

#2723

[kylekatarnls]

Hello because of this:
#2723 (comment)

We shouldn't make any explicit cast here, or else we should add first an input validation with a specific error such as "string" is not a valid numeric value.

Because muting the error and simply replacing any non-numeric string with 0 is just hiding to the developer the incorrect usage and cause bugs later.