set default extras as empty array to prevent compact() errors

[kilip]

Hello,

PHP compact() function at line 413 will create php error when $args is an empty array:

zend-view/src/Helper/HeadLink.php

Lines 379 to 416 in 34babb4

	public function createDataStylesheet(array $args)
	{
	$rel = 'stylesheet';
	$type = 'text/css';
	$media = 'screen';
	$conditionalStylesheet = false;
	$href = array_shift($args);
	if ($this->isDuplicateStylesheet($href)) {
	return false;
	}
	if ($args) {
	$media = array_shift($args);
	if (is_array($media)) {
	$media = implode(',', $media);
	} else {
	$media = (string) $media;
	}
	}
	if ($args) {
	$conditionalStylesheet = array_shift($args);
	if (! empty($conditionalStylesheet) && is_string($conditionalStylesheet)) {
	$conditionalStylesheet = (string) $conditionalStylesheet;
	} else {
	$conditionalStylesheet = null;
	}
	}
	if ($args && is_array($args[0])) {
	$extras = array_shift($args);
	$extras = (array) $extras;
	}
	$attributes = compact('rel', 'type', 'href', 'media', 'conditionalStylesheet', 'extras');
	return $this->createData($attributes);
	}

I have found this error in this travis build:
https://travis-ci.org/cross-solution/YAWIK/jobs/453775095#L1805
To reproducing error just simply execute this function HeadLink::prependStylesheet('/some/foo.css')

I think this compact() error only occurs in php 7.3, but the code is buggy too. We need to define default value for $extras variables.

[froschdesign]

Reference for this change in PHP 7.3: http://php.net/manual/en/function.compact.php#refsect1-function.compact-changelog

[froschdesign]

Duplicate of #167

[weierophinney]

Thanks, @kilip - cherry-picked to master, to release with 2.10.1.