PointBasedMeasure crashes when input images have very little texture

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Process two images with PointBasedMeasure that have virtually no texture.

What is the expected output? What do you see instead?
findEdges should report that there is no edge for that image pair. Instead, it 
reports one of the following, depending on the randsample function that is 
accessed:

??? Index exceeds matrix dimensions.
Error in ==> ransac>randsample at
229
  r=r(1:s);

OR

error('At least 8 points are needed to compute the fundamental matrix');

Original issue reported on code.google.com by dddvis...@gmail.com on 11 Dec 2012 at 8:19