Error in Physics system: not in entity map

[Diego Ferigo]

With the most recent devel version, running a simulation with ScenarIO Gazebo results in a long list of the following error:

[Err] [Physics.cc:2163] Internal error: link [876] not in entity map
[Err] [Physics.cc:2163] Internal error: link [878] not in entity map
[Err] [Physics.cc:2163] Internal error: link [880] not in entity map
[Err] [Physics.cc:2163] Internal error: link [882] not in entity map
[Err] [Physics.cc:2163] Internal error: link [885] not in entity map
[Err] [Physics.cc:2163] Internal error: link [887] not in entity map
[Err] [Physics.cc:2163] Internal error: link [890] not in entity map
[Err] [Physics.cc:2163] Internal error: link [892] not in entity map

I open this issue only as a reminder and for future reference. The setup where this is occurring has an updated ScenarIO version but an outdated Ignition Gazebo version, old enough to miss the support of preventing the default loading of the server plugins #289.

In general, this error will occur if the upstream Physics system is somehow loaded instead of our vendored system. In the setup described above, this was loaded from the server.config (behavior disabled in #379):

[Msg] No systems loaded from SDF, loading defaults
[Dbg] [ServerConfig.cc:920] Loaded (3) plugins from file [/home/dferigo/.ignition/gazebo/server.config]
[Dbg] [Physics.cc:687] Loaded [ignition::physics::dartsim::Plugin] from library [/usr/local/src/workspace/install/lib/ign-physics-4/engine-plugins/libignition-physics-dartsim-plugin.so]

If this happens on your system, make sure that the correct Physics system is loaded.