Methanal.View.IntegerInput discards a valid value of 0 when an embedded label is provided for the field

[Forrest Aldridge]

The method Methanal.View.TextInput._needsLabel replaces valid values of 0 with the embedded label for the input if provided, because it only tests whether the raw value evaluates to false in a boolean context.

The attached patch first converts the value to a string if it is not null and then checks whether the string has a length of 0.