field must be a valid integer or decimal for non required field

I have a bug in my configuration where I'm using a the widget "Select (or other) list" on a non-required "float" field.
When an editor is leaving the field blank (using "- None -") it triggered the validation error: FieldName field must be a valid integer or decimal.
I tracked down the issue to the function select_or_other_field_widget_validate(): where the following if condition is TRUE, but IMO it shouldn't.

if ($value !== "") {
}

Im my case the $value contains no data BUT it is not a string!
I'm suggesting to apply the following condition instead:

if ($value != "") {
}

(PS: I'm running PHP 7.0.x, maybe it does matter...)