In SharePoint 2013 server side object model (SSOM), it appears that the Method overloads of the SPGroupCollection such as GetByName() or indexer all throw an exception when the group is not found.  However, you can still use reflection to get non throwing version of the methods. In my project I ended up creating an extension method that wraps the reflection based function call.

public static class SPGroupCollectionExtensions
{
  public static SPGroup GetByNameNoThrow(this SPGroupCollection group, string groupName)
  {
    var method = group.GetType().GetMethod("GetByNameNoThrow", BindingFlags.Instance | BindingFlags.NonPublic);
var parameters = new object[] {groupName};
    return (SPGroup)method.Invoke(group, parameters);
   }
}