This object was throwing away the wrong vector the first time

it started to prune the set of independent vectors.  All subsequent
prunings were right, just not the first one.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402927

dlib/svm/linearly_independent_subset_finder.h

@@ -135,6 +135,9 @@ namespace dlib
                 {
                     if (dictionary.size() == my_max_dictionary_size)
                     {
+                        // if we have never computed the min_strength then we should compute it 
+                        if (min_strength == 0)
+                            recompute_min_strength();
 
                         const long i = min_vect_idx;