various particle crash and deadlock fixes

interface/src/ParticleTreeRenderer.cpp

@@ -33,10 +33,7 @@ void ParticleTreeRenderer::init() {
 void ParticleTreeRenderer::update() {
     if (_tree) {
         ParticleTree* tree = static_cast<ParticleTree*>(_tree);
-        if (tree->tryLockForWrite()) {
-            tree->update();
-            tree->unlock();
-        }
+        tree->update();
     }
 }
 

libraries/octree/src/OctreeElement.cpp

@@ -739,7 +739,7 @@ void OctreeElement::setChildAtIndex(int childIndex, OctreeElement* child) {
         _externalChildrenMemoryUsage += NUMBER_OF_CHILDREN * sizeof(OctreeElement*);
 
     } else if (previousChildCount == 2 && newChildCount == 1) {
-        assert(child); // we are removing a child, so this must be true!
+        assert(!child); // we are removing a child, so this must be true!
         OctreeElement* previousFirstChild = _children.external[firstIndex];
         OctreeElement* previousSecondChild = _children.external[secondIndex];
         delete[] _children.external;

libraries/particles/src/ParticleTree.cpp

@@ -487,7 +487,9 @@ void ParticleTree::update() {
     }
 
     // prune the tree...
+    lockForWrite();
     recurseTreeWithOperation(pruneOperation, NULL);
+    unlock();
 }
 
 

libraries/particles/src/ParticlesScriptingInterface.h

@@ -30,12 +30,10 @@ public:
 private slots:
     /// inbound slots for external collision systems
     void forwardParticleCollisionWithVoxel(const ParticleID& particleID, const VoxelDetail& voxel) {
-        qDebug() << "forwardParticleCollisionWithVoxel()";
         emit particleCollisionWithVoxel(particleID, voxel);
     }
 
     void forwardParticleCollisionWithParticle(const ParticleID& idA, const ParticleID& idB) {
-        qDebug() << "forwardParticleCollisionWithParticle()";
         emit particleCollisionWithParticle(idA, idB);
     }