I believe the problem is not that different icons are being shown for different filetypes, but that multiple instances of the icon for Olular are being displayed in the Unity Launcher because BAMF is reporting these as different applications (not as different instances of the same application).
I believe the problem is not that different icons are being shown for different filetypes, but that multiple instances of the icon for Olular are being displayed in the Unity Launcher because BAMF is reporting these as different applications (not as different instances of the same application).