validate link has parent

Author: MarqRazz

moveit_core/robot_model/src/joint_model_group.cpp

@@ -229,8 +229,9 @@ JointModelGroup::JointModelGroup(const std::string& group_name, const srdf::Mode
   {
     link_model_map_[link_model->getName()] = link_model;
     link_model_name_vector_.push_back(link_model->getName());
-    // if this is the first link of the group with geometry (for example `base_link`) it should included
-    if (link_model_with_geometry_vector_.empty() && !link_model->getParentLinkModel()->getShapes().empty())
+    // if this is the first link of the group with a valid parent and includes geometry (for example `base_link`) it should included
+    if (link_model_with_geometry_vector_.empty() && link_model->getParentLinkModel() &&
+        !link_model->getParentLinkModel()->getShapes().empty())
     {
       link_model_with_geometry_vector_.push_back(link_model->getParentLinkModel());
       link_model_with_geometry_name_vector_.push_back(link_model->getParentLinkModel()->getName());