Use first limit as default in ProductFilter

[fritzmg]

If you have multiple product or category filters on the page and one of the product filters has iso_enableLimit enabled then filtering might not work in general.

What happens is that you are first redirected to e.g. products?isorc=20 and then back to e.g. products?isorc=1, completely ignoring the filter configuration of the request cache ID 20. This can happen if the config ID 20 does not contain a limit from the product filter module that has iso_enableLimit enabled.

The ProductFilter module then thinks the config is wrong and executes:

core/system/modules/isotope/library/Isotope/Module/ProductFilter.php

Lines 466 to 474 in a23ea30

	} elseif ($objLimit->notIn($arrLimit)) {
	// Request cache contains wrong value, delete it!
	$this->blnUpdateCache = true;
	Isotope::getRequestCache()->setLimitForModule(Limit::to($arrLimit[0]), $this->id);
	RequestCache::deleteById(Input::get('isorc'));
	} elseif (!$this->blnUpdateCache) {

This then enables $this->blnUpdateCache = true; and thus the filter will redirect to another request cache URL.

This PR fixes that by using the first limit value as the default when fetching getFirstLimitForModules() from the request cache.

[aschempp]

Why are you being redirected to products?isorc=20 in the first place?

[fritzmg]

That's the normal behaviour of the filter modules. The CategoryFilter generates links like /foobar?categoryfilter=… (see here) - and these URLs then save the filter configuration into tl_iso_requestcache and then redirect to a /foobar?isorc=… URL.