Only try to flush views cache if views module is enabled

Problem

When Views is not enabled and we trigger the clear cache button we get this error

PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'drupal_distro.cache_views' doesn't exist: DELETE FROM {cache_views} WHERE (cid LIKE :db_condition_placeholder_0 ESCAPE '\\') ; Array ( [:db_condition_placeholder_0] => powered-by% ) in cache_clear_all() (line 176 of /vagrant/repos/dennis_distro_7/includes/cache.inc).

Proposed solution

Check if views is enabled