That's not a good source because it doesn't contain all European countries. Countries such as Russia and Bosnia-Herzegovina should definitely be on the list.
They are actually non-Islamic countries. Both Turkey and Albania do not have any state religion, technically making them non-Islamic, therefore they should be on the list.
They have both had significant Muslim populations for a long time, Russia since the 7th century AD, and have settled there since, and Bosnia and Herzegovina since the 15th-16th century AD.
As others have mentioned, Albania has a population of almost 2.9 million and is 57% Muslim, so it should definitely be on this list, along with a few other countries.