Fix TSAN warnings for ripples emitter

While main thread creates particles rendering thread draws them so
sychronization is required.

apps/openmw/mwrender/ripplesimulation.cpp

@@ -200,6 +200,7 @@ void RippleSimulation::emitRipple(const osg::Vec3f &pos)
 {
     if (std::abs(pos.z() - mParticleNode->getPosition().z()) < 20)
     {
+        osgParticle::ParticleSystem::ScopedWriteLock lock(*mParticleSystem->getReadWriteMutex());
         osgParticle::Particle* p = mParticleSystem->createParticle(nullptr);
         p->setPosition(osg::Vec3f(pos.x(), pos.y(), 0.f));
         p->setAngle(osg::Vec3f(0,0, Misc::Rng::rollProbability() * osg::PI * 2 - osg::PI));