The WMS GetFeatureInfo returns an empty collection when querying a point layer that has a style the uses the sld:ElseFilter.
In GeoServer 2.9.0 it works as expected but in 2.11.1, 2.11.2 and 2.12-RC1 it does not.
I have reproduced this using the Manhattan (NY) points of interest demo layer in layer preview with the following style:
Steps to reproduce:
1. Using GeoServer 2.12-RC1 and the demo data
2. Edit the poi style, replace with above style
3. Open Manhattan (NY) points of interest as OpenLayers map in Layer preview
4. Click on the circle (art), feature information is displayed
5. Click on any square, no feature information is displayed