fix(rss) Add parentheses to nested ternery operator

[tstephen]

Types of changes:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project. (WPCS)
• My change requires a change to the documentation.

Brief description of the proposed change:

Resolves

Fatal error: Unparenthesized `a ? b : c ? d : e` is not supported. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` in /wp-content/plugins/sermon-manager-for-wordpress/views/wpfc-podcast-feed.php on line 165

reported as issue #299.

Any other info: