SURF feature detector exception

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C#

Emgu-CV

Hi i'm doing a project requires Template matching using EmguCv
the Surf Detector example in Emgu and it's working Well
but the problem here when i trying to enter a small templates to search within the Full image and it gives me this exception

SEHException was unhanded
External component has thrown an exception

in this line

nonZeroCount = Features2DTracker.VoteForSizeAndOrientation(modelKeyPoints, observedKeyPoints, indices, mask, 1.5,1);

so how to handle it and handle the code to accept searching wish small templates