Fix Eigen error in 2D sphere manifolds
Since Eigen does not allow to have a RowMajor column vector (see
https://gitlab.com/libeigen/eigen/-/issues/416), the storage order
must be set to ColMajor in that case. This fix adds that special
case when generating 2D sphere manifolds.

Change-Id: I594932e0dafc878e0b348f72524478588e61b34d

include/ceres/sphere_manifold.h

diff --git a/include/ceres/sphere_manifold.h b/include/ceres/sphere_manifold.h
index 5d71cbb..1189c11 100644
--- a/include/ceres/sphere_manifold.h
+++ b/include/ceres/sphere_manifold.h
@@ -114,12 +114,17 @@
   static constexpr int TangentSpaceDimension =
       AmbientSpaceDimension > 0 ? AmbientSpaceDimension - 1 : Eigen::Dynamic;
 
+  // NOTE: Eigen does not allow to have a RowMajor column vector.
+  // In that case, change the storage order
+  static constexpr int SafeRowMajor =
+      TangentSpaceDimension == 1 ? Eigen::ColMajor : Eigen::RowMajor;
+
   using AmbientVector = Eigen::Matrix<double, AmbientSpaceDimension, 1>;
   using TangentVector = Eigen::Matrix<double, TangentSpaceDimension, 1>;
   using MatrixPlusJacobian = Eigen::Matrix<double,
                                            AmbientSpaceDimension,
                                            TangentSpaceDimension,
-                                           Eigen::RowMajor>;
+                                           SafeRowMajor>;
   using MatrixMinusJacobian = Eigen::Matrix<double,
                                             TangentSpaceDimension,
                                             AmbientSpaceDimension,