Fix off by one error in the polynomial solver

Change-Id: I682525a911ce62b6e057072ce396723c7249df1b

internal/ceres/polynomial_solver.cc

diff --git a/internal/ceres/polynomial_solver.cc b/internal/ceres/polynomial_solver.cc
index 91c6001..03f63e6 100644
--- a/internal/ceres/polynomial_solver.cc
+++ b/internal/ceres/polynomial_solver.cc
@@ -106,7 +106,7 @@
   companion_matrix.resize(degree, degree);
   companion_matrix.setZero();
   companion_matrix.diagonal(-1).setOnes();
-  companion_matrix.col(degree-1) = -polynomial.reverse().head(degree-1);
+  companion_matrix.col(degree-1) = -polynomial.reverse().head(degree);
 }
 
 // Remove leading terms with zero coefficients.