Steps to reproduce:

1. Navigate to Space Tools -> Look and Feel -> Sidebar, header, and footer submenu
2. Insert 'Content by Label' macro markup as follows, with existing label substituted for <existingLabel> into Sidebar:

{contentbylabel:labels=<existingLabel>|showLabels=false|showSpace=false|max=100}

3. Observe following error messaging:

Error formatting macro: contentbylabel: com.atlassian.confluence.api.service.exceptions.BadRequestException: Could not parse cql : null

Additional notes:

• Other macros that appear to rely on CQL appear to be unaffected
• Content by Label macro works within page using the same markup
• Similar error messaging given when used within Header or Footer areas