fixed ASSERT and last commit's oopsie

src/helpers/SubsurfaceTree.cpp

@@ -56,6 +56,16 @@ SSurfaceTreeNode* SubsurfaceTree::createTreeRoot(wlr_surface* pSurface, applyGlo
 void destroySubsurface(SSubsurface* pSubsurface);
 
 void SubsurfaceTree::destroySurfaceTree(SSurfaceTreeNode* pNode) {
+    bool exists = false;
+    for (auto& n : surfaceTreeNodes) {
+        if (&n == pNode) {
+            exists = true;
+            break;
+        }
+    }
+
+    RASSERT(exists, "Tried to delete a surfaceTreeNode that doesn't exist!");
+
     for (auto& c : pNode->childSubsurfaces)
         destroySubsurface(&c);
 
@@ -160,4 +170,4 @@ void Events::listener_destroySubsurfaceNode(wl_listener* listener, void* data) {
     wl_list_remove(&pNode->listen_destroy.link);
 
     SubsurfaceTree::surfaceTreeNodes.remove(*pNode);
-}
+}