I dug into the reason. It's because some search results in the API response array do not have 'bounds' e.g. "Oxford, Roger Dudon Way" is coming through without this field.
I don't know if that is a new bug in your main API, or maybe this javascript should tolerate missing bounds. If it's the latter, then I have the fix
The demo here is broken: http://geocoder.opencagedata.com/code/leaflet-demo.html ...for the majority of searches I'm testing with. e.g. just searching for "Oxford"
I dug into the reason. It's because some search results in the API response array do not have 'bounds' e.g. "Oxford, Roger Dudon Way" is coming through without this field.
I don't know if that is a new bug in your main API, or maybe this javascript should tolerate missing bounds. If it's the latter, then I have the fix