Merge branch 'ceres_manager_fix' into 'master'

small fix in ceres_manager constructor

See merge request mobile_robotics/wolf!206

src/ceres_wrapper/ceres_manager.cpp

@@ -7,7 +7,7 @@
 
 namespace wolf {
 
-CeresManager::CeresManager(ProblemPtr& _wolf_problem,
+CeresManager::CeresManager(const ProblemPtr& _wolf_problem,
                            const ceres::Solver::Options& _ceres_options) :
   SolverManager(_wolf_problem),
   ceres_options_(_ceres_options)

src/ceres_wrapper/ceres_manager.h

@@ -40,7 +40,7 @@ protected:
 
 public:
 
-  CeresManager(ProblemPtr& _wolf_problem,
+  CeresManager(const ProblemPtr& _wolf_problem,
                const ceres::Solver::Options& _ceres_options
                 = ceres::Solver::Options());