Can't delete calendars

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Using the core Calendar, I am unable to delete calendars.
Go to /dashboard/calendar/event_list, select the calendar from the drop down then select Delete Calendar. Dialog "Are you sure? This action cannot be undone", I click Delete Calendar but the calendar is not deleted.
There are no events in the calendars I'm trying to delete.


Status: New
simonchilton

concrete5 Environment Information

# concrete5 Version
Core Version - 8.4.4
Version Installed - 8.4.4
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Backbone (1.0.2), ExchangeCore reCAPTCHA (1.1.1), HTML+PHP Code Block (1.0.1), Login Dialog (0.9.7), Raptorize (2.0)

# concrete5 Overrides
blocks/calendar_event/templates/thumbnail.php, blocks/calendar_event/templates, blocks/calendar_event, blocks/event_list/templates/thumbnail.php, blocks/event_list/templates, blocks/event_list, blocks/content/templates/event_post/view.php, blocks/content/templates/event_post/view.css, blocks/content/templates/event_post, blocks/content/templates, blocks/content

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Apache

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cgi-fcgi

# PHP Version
5.6.37

# PHP Extensions
bcmath, bz2, calendar, cgi-fcgi, Core, ctype, curl, date, dom, ereg, exif, fileinfo, filter, ftp, gd, gettext, hash, iconv, imagick, imap, intl, json, ldap, libxml, mbstring, mcrypt, mhash, mysql, mysqli, mysqlnd, OAuth, openssl, pcre, PDO, pdo_mysql, pdo_pgsql, pdo_sqlite, pgsql, Phar, posix, readline, Reflection, session, SimpleXML, soap, sockets, SPL, sqlite3, standard, tokenizer, wddx, xdebug, xml, xmlreader, xmlwriter, xsl, zip, zlib

# PHP Settings
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log_errors_max_len - 1024
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Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:64.0) Gecko/20100101 Firefox/64.0