Transform objective function in osr to full matrix

If the objective function only has one element, the scalar product of a sparse matrix and a full matrix is sparse (in contrast to two or more elements). This crashes the osr code subsequently.

matlab/osr_obj.m

@@ -86,4 +86,4 @@ switch info(1)
 end
 
 vx = get_variance_of_endogenous_variables(dr,i_var);
-loss = weights(:)'*vx(:);
+loss = full(weights(:)'*vx(:));