[7.x] Fixed isEmpty implementation

[GrahamCampbell]

Do we really want '0' to be treated as an empty html string?

I don't even understand why isEmpty was added. Why not just compare its value with the empty string. In particular, this method is not present on the htmlable contract, so cannot usually be safely called anyway...

I'd actually vote for just entirely removing this method.

[GrahamCampbell]

Should we actually remove this method?

$v->toHtml() === '' is clearer than $v->isEmpty() IMO.

[vlakoff]

Note it broke consistency with Stringable::isEmpty, which still has the "wrong behaviour".

'0' definitely shouldn't be considered to be an empty string.

But doing the change in Stringable::isEmpty would be a BC break. Though, as it's a recent class (and the "correct behaviour" is probably what the users would expect), maybe it's still time for just doing the change. I don't think it's a change of behaviour, but really a bugfix.

[mvdnbrk]

@vlakoff submitted #32447 to fix the behaviour of the isEmpty method in the Stringable class.