Error when adding WMS layer to GeoNetwork Map - "no tile URL found"

**Describe the bug**
When I try to add a layer to map I got the following error messages:

Something went wrong while loading tile'- no tile URL found- ...'

but it is strange because if I zoom to the layer it is there.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to 'Map'
2. Click on '+' sign and then "Search" to get the list of the existing layer
3. Choose one of them
4. The error appears in a popup

**Expected behavior**
The layer should appear on the map and the possibility to zoom to it should work

**Screenshots**

**Desktop (please complete the following information):**
- Browser: Firefox
- GeoNetwork Version 3.8
- Server Application Tomcat 7.0.76

**Additional context**
Sometimes it seems that this error appears when you try to use this functionality the first time; then it works when you add a second layer. But it is a random behavior.

Start by reproducing the Map flow with an existing WMS layer, including the first and second layer additions, and observe the tile-loading request behind the popup. Trace where the tile URL is obtained and verify the fix by confirming that the layer renders without the error and that zooming to it still works.

Written by the indexing model from the issue text.