Description

A few sentences describing the overall goals of the issue.

In case of Bug (otherwise remove this paragraph)

Browser Affected
(use this site: https://www.whatsmybrowser.org/ for non expert users)

• Internet Explorer
• Chrome
• Firefox
• Safari

Browser Version Affected

• Chrome v66

Steps to reproduce

• open a map with vector layers (at least one)
• open TOC
• select a vector layer
• open feature grid
• open advanced search
• select a target layer in Layer filter
• leave operation field empty
• click on search

Expected Result

• No error in console

Current Result

• Error in console
  Uncaught TypeError: h[e.operation] is not a function
  at Object.processOGCCrossLayerFilter

Other useful information (optional):