Avoid nullptr dereference if TouchPlugin is not attached to a model entity.

[jrutgeer]

🦟 Bug fix

Summary

Two small fixes:

• Avoid nullptr dereference in case the plugin is not attached to a model (as sdfConfig is initialized only if TouchPlugin::Configure() is successful, see code snippet below),
• Avoid execution of preUpdate() code if the system was not initialized correctly.

I also changed the documentation somewhat to better explain what the plugin actually does.

gz-sim/src/systems/touch_plugin/TouchPlugin.cc

Lines 358 to 370 in f2ff574

	void TouchPlugin::Configure(const Entity &_entity,
	const std::shared_ptr<const sdf::Element> &_sdf,
	EntityComponentManager &_ecm, EventManager &)
	{
	this->dataPtr->model = Model(_entity);
	if (!this->dataPtr->model.Valid(_ecm))
	{
	gzerr << "Touch plugin should be attached to a model entity. "
	<< "Failed to initialize." << std::endl;
	return;
	}
	this->dataPtr->sdfConfig = _sdf->Clone();
	}

[azeey]

Good catch. Thanks!

[codecov]

Codecov Report

Merging #2069 (3ee204d) into gz-sim7 (50a99e6) will decrease coverage by 0.13%.
Report is 21 commits behind head on gz-sim7.
The diff coverage is 100.00%.

❗ Current head 3ee204d differs from pull request most recent head 42bf976. Consider uploading reports for the commit 42bf976 to get more accurate results

@@             Coverage Diff             @@
##           gz-sim7    #2069      +/-   ##
===========================================
- Coverage    65.00%   64.88%   -0.13%     
===========================================
  Files          354      354              
  Lines        28667    28688      +21     
===========================================
- Hits         18636    18613      -23     
- Misses       10031    10075      +44     

Files Changed	Coverage Δ
include/gz/sim/ServerConfig.hh	100.00% <ø> (ø)
include/gz/sim/rendering/MarkerManager.hh	100.00% <ø> (ø)
src/LevelManager.cc	89.39% <ø> (ø)
src/systems/touch_plugin/TouchPlugin.hh	100.00% <ø> (ø)
src/systems/physics/Physics.cc	67.78% <100.00%> (+0.45%)	⬆️
src/systems/touch_plugin/TouchPlugin.cc	87.40% <100.00%> (ø)

... and 2 files with indirect coverage changes

[azeey]

#2070 seems to have fixed the ABI failure.