When performing a search on Actions -> Pages for filtering with a regex, providing an invalid regex causes the UI to show an exception:
An example is: sometext, as you can see * should appear after some character so the regex ends up crashing server.
The error message visible is as follows:
There is an error. Please report the message (Piwik 2.1.0) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).
Warning: preg_match(): Compilation failed: nothing to repeat at offset 0 in /var/www/html/piwik/core/DataTable/Filter/Pattern.php on line 72
Backtrace -->
#0 Piwik\Error::errorHandler(…) called at [:]
#1 preg_match(…) called at [/var/www/html/piwik/core/DataTable/Filter/Pattern.php:72]
#2 Piwik\DataTable\Filter\Pattern::match(…) called at [/var/www/html/piwik/core/DataTable/Filter/PatternRecursive.php:80]
#3 Piwik\DataTable\Filter\PatternRecursive->filter(…) called at [/var/www/html/piwik/core/DataTable.php:424]
#4 Piwik\DataTable->filter(…) called at [/var/www/html/piwik/core/API/DataTableGenericFilter.php:143]
#5 Piwik\API\DataTableGenericFilter->applyGenericFilters(…) called at [/var/www/html/piwik/core/API/DataTableGenericFilter.php:37]
#6 Piwik\API\DataTableGenericFilter->filter(…) called at [/var/www/html/piwik/core/Plugin/Visualization.php:556]
#7 Piwik\Plugin\Visualization->applyGenericFilters(…) called at [/var/www/html/piwik/core/Plugin/Visualization.php:309]
#8 Piwik\Plugin\Visualization->applyFilters(…) called at [/var/www/html/piwik/core/Plugin/Visualization.php:171]
#9 Piwik\Plugin\Visualization->buildView(…) called at [/var/www/html/piwik/core/Plugin/ViewDataTable.php:358]
#10 Piwik\Plugin\ViewDataTable->render(…) called at [/var/www/html/piwik/core/Plugin/Controller.php:228]
#11 Piwik\Plugin\Controller->renderReport(…) called at [/var/www/html/piwik/plugins/Actions/Controller.php:89]
#12 Piwik\Plugins\Actions\Controller->getPageUrls(…) called at [:]
#13 call_user_func_array(…) called at [/var/www/html/piwik/core/FrontController.php:521]
#14 Piwik\FrontController->doDispatch(…) called at [/var/www/html/piwik/core/FrontController.php:84]
#15 Piwik\FrontController->dispatch(…) called at [/var/www/html/piwik/core/dispatch.php:30]
#16 require_once(…) called at [/var/www/html/piwik/index.php:47]