ajkopinga/openlayers — comment on commit 7e878cc6247b5d2126d2c4fe568a4fd0e6284f48
File:  line 0
By ajkopinga:

No, it should be ===, because if the root (the canvas for the features) is invisible (display:none), getFeatureIdFromEvent should return immediately. At that point feature is still undefined, so any select/click control won't pick up anything.

I'll look into writing a unit test for this.