IsFloat validator should return a standard error message for empty strings

[froschdesign]

Q	A
Documentation	no
Bugfix	yes
BC Break	no
New Feature	no
RFC	no
QA	no

Description

The following code throws an AssertionError:

$validator = new Laminas\I18n\Validator\IsFloat();
var_dump($validator->isValid(''));

Fatal error: Uncaught AssertionError: assert($lastStringGroup !== '') in /src/Validator/IsFloat.php:242

laminas-i18n/src/Validator/IsFloat.php

Lines 233 to 242 in 4f23433

	// No strrpos() in wrappers yet. ICU 4.x doesn't have grouping size for
	// everything. ICU 52 has 3 for ALL locales.
	$groupSize = $formatter->getAttribute(NumberFormatter::GROUPING_SIZE) ?: 3;
	assert(is_int($groupSize));
	$lastStringGroup = $this->wrapper->strlen($value) > $groupSize ?
	$this->wrapper->substr($value, 0 - $groupSize) :
	$value;
	assert(is_string($lastStringGroup));
	assert($lastStringGroup !== '');

These lines were introduced with #104: 5062ef1

In previous versions this was not a problem:

$validator = new Laminas\I18n\Validator\IsFloat();
var_dump($validator->isValid('')); // false
var_dump($validator->getMessages()); ['notFloat' => 'The input does not appear to be a float']

[gsteel]

@froschdesign
Look good to you? I can't request your review because you opened the patch!

[froschdesign]

@gsteel
Thank you for your help! 👍🏻