Avoid PHP notices on activity form

[braders]

Overview

Avoid PHP notices on activity form.

This ensures that fallback values are set, so that notices are not thrown when activity.tpl does {if} checks on $activityTypeDescription and $activityTypeNameAndLabel.machineName.

Before

When creating a new activity (/civicrm/activity) a handful of PHP notices were generated from within Smarty templates.

After

No notices generated by core on this form.

[civibot]

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