fix(editor): guard the places where the editor could crash outright

Found with an address and undefined behaviour sanitizer build, random
monkey sessions on the test sceneries and broken inputs:

- A deleted model left its pointer in the pick list of the renderer, the
  bound node of the panels, the bindings of the infrastructure and the
  selection: the next pick or panel frame read freed memory. The renderer
  forgets it, and one erase_model does the cleaning for all the places
  which deleted a model by hand.
- The plan band of a route read the vertex before the first one in the
  frame a drag was let go.
- A scenery which can't be opened goes back to the launcher with the
  reason in the log, a track of an unknown type or a tributary loads as
  a normal track or a river with a message, and a spline with no finite
  length or step gets a sane number of segments.
- Typed numbers which aren't (NaN, inf, ends 0 m or 1000 km apart, a
  vector of 1e30, a diverging track part of 5 km, a curve threshold of 0,
  a zero history size, radius norms below zero) are refused or clamped,
  where they made the geometry run away or divide by zero.
- Folders which can't be read and file names which aren't valid in the
  locale no longer throw out of the scans of sceneries, textures, sweeps,
  roads and signal plates; the scans skip them.
- The launcher: Ctrl+Del with no trainset selected, a dropped vehicle
  whose skin is gone and a text with a percent sign.
- A terrain mesh made for another resolution of its chunk isn't put into
  the chunk, and a slot is reused only for a mesh of the same size.
- Vehicles on a track changed by the editor are moved over a copy of the
  list they leave.
- The table of the keyboard shortcuts gives its stretched column a
  weight, else ImGui divides 0 by 0 in the first frame of the window.

launcher/scenery_list.cpp

@@ -23,7 +23,7 @@ bool ui::scenerylist_panel::on_key(int key, int action)
 	if (it == keyboard.keytonamemap.end())
 		return false;
 
-	if (Global.ctrlState && it->second == "delete")
+	if (Global.ctrlState && it->second == "delete" && selected_trainset != nullptr)
 		purge_selected_trainset();
 
 	return true;
@@ -117,7 +117,7 @@ void ui::scenerylist_panel::draw_launch_box()
 {
 	ImGui::NextColumn();
 
-	ImGui::TextWrapped(selected_trainset->description.c_str());
+	ImGui::TextWrapped("%s", selected_trainset->description.c_str());
 
 	ImGui::Checkbox(STR_C("Trainset turned around"), &selected_trainset->reversed);
 	if (ImGui::IsItemHovered())
@@ -283,7 +283,8 @@ void ui::scenerylist_panel::draw_trainset(trainset_desc &trainset)
 	draw_droptarget(trainset, position++);
 	ImGui::SameLine(15.0f);
 
-	for (auto &dyn_desc : trainset.vehicles) {
+	for (std::size_t index = 0; index < trainset.vehicles.size(); ++index) {
+		auto &dyn_desc = trainset.vehicles[index];
 		deferred_image *mini = nullptr;
 
 		if (dyn_desc.skin && dyn_desc.skin->mini.get() != deferred_image::invalid_id)
@@ -345,16 +346,19 @@ void ui::scenerylist_panel::draw_droptarget(trainset_desc &trainset, int positio
 		if (payload) {
 			skin_set *ptr = *reinterpret_cast<skin_set **>(payload->Data);
 			std::shared_ptr<skin_set> skin;
-			for (auto &s : ptr->vehicle.lock()->matching_skinsets)
-				if (s.get() == ptr)
-					skin = s;
+			if (auto const vehicle = ptr->vehicle.lock())
+				for (auto &s : vehicle->matching_skinsets)
+					if (s.get() == ptr)
+						skin = s;
 
-			trainset.vehicles.emplace(trainset.vehicles.begin() + position);
-			dynamic_desc &desc = trainset.vehicles[position];
+			if (skin) {
+				trainset.vehicles.emplace(trainset.vehicles.begin() + position);
+				dynamic_desc &desc = trainset.vehicles[position];
 
-			desc.name = skin->skin + "_" + std::to_string((int)LocalRandom(0.0, 10000000.0));
-			desc.vehicle = skin->vehicle.lock();
-			desc.skin = skin;
+				desc.name = skin->skin + "_" + std::to_string((int)LocalRandom(0.0, 10000000.0));
+				desc.vehicle = skin->vehicle.lock();
+				desc.skin = skin;
+			}
 		}
 
 		payload = ImGui::AcceptDragDropPayload("vehicle_set");
@@ -368,7 +372,7 @@ void ui::scenerylist_panel::draw_droptarget(trainset_desc &trainset, int positio
 				if (moved->position < position)
 					offset = -1;
 			} else {
-				desc_copy.name = desc_copy.skin->skin + "_" + std::to_string((int)LocalRandom(0.0, 10000000.0));
+				desc_copy.name = (desc_copy.skin ? desc_copy.skin->skin : desc_copy.name) + "_" + std::to_string((int)LocalRandom(0.0, 10000000.0));
 			}
 
 			trainset.vehicles.insert(trainset.vehicles.begin() + position + offset, desc_copy);

launcher/scenery_scanner.cpp

@@ -10,13 +10,21 @@ scenery_scanner::scenery_scanner(ui::vehicles_bank &bank)
 
 void scenery_scanner::scan()
 {
-	for (auto &f : std::filesystem::directory_iterator("scenery")) {
-		std::filesystem::path path(std::filesystem::relative(f.path(), "scenery/"));
+	std::error_code error;
+	for (std::filesystem::directory_iterator f{"scenery", std::filesystem::directory_options::skip_permission_denied, error}, end; f != end; f.increment(error)) {
+		std::filesystem::path path(std::filesystem::relative(f->path(), "scenery/", error));
+		std::string name;
+		try {
+			name = path.string();
+		}
+		catch (std::exception const &) {
+			continue;
+		}
 
-		if (*path.filename().string().begin() == '$')
+		if (name.empty() || path.filename().string().front() == '$')
 			continue;
 
-		if (path.string().ends_with(".scn"))
+		if (name.ends_with(".scn"))
 			scan_scn(path);
 	}
 

launcher/textures_scanner.cpp

@@ -4,12 +4,13 @@
 
 void ui::vehicles_bank::scan_textures()
 {
-	for (auto &f : std::filesystem::recursive_directory_iterator("dynamic")) {
-		if (f.path().filename() != "textures.txt")
+	std::error_code error;
+	for (std::filesystem::recursive_directory_iterator f{"dynamic", std::filesystem::directory_options::skip_permission_denied, error}, end; f != end; f.increment(error)) {
+		if (f->path().filename() != "textures.txt")
 			continue;
 
-		std::fstream stream(f.path(), std::ios_base::binary | std::ios_base::in);
-		ctx_path = std::filesystem::relative(f.path().parent_path(), "dynamic/");
+		std::fstream stream(f->path(), std::ios_base::binary | std::ios_base::in);
+		ctx_path = std::filesystem::relative(f->path().parent_path(), "dynamic/", error);
 
 		std::string line;
 		while (std::getline(stream, line))