Fixes #639: mapping mime types to extensions via registry could make …

…problems

src/Libraries/SmartStore.Core/IO/MimeTypes.cs

@@ -40,7 +40,7 @@ public static string MapMimeTypeToExtension(string mimeType)
 						result = value != null ? value.ToString().Trim('.') : null;
 					}
 				}
-				catch (SecurityException)
+				catch
 				{
 					string[] parts = mimeType.Split('/');
 					result = parts[parts.Length - 1];