defensive check on sermons_array

[tstephen]

Types of changes:

• [X ] 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:

• [X ] 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:

Fix for issue 291

Any other info:

Doesn't identify the root cause of the empty array.