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.

application/editormodeinfra.cpp

@@ -97,6 +97,11 @@ class live_nodes
 	{
 		return Node != nullptr && m_nodes.count(Node) > 0;
 	}
+	void forget(scene::basic_node const *Node)
+	{
+		m_nodes.erase(Node);
+		m_valid = false;
+	}
 
   private:
 	std::unordered_set<scene::basic_node const *> m_nodes;
@@ -778,6 +783,17 @@ void editor_mode::infra_load()
 	         logtype::generic);
 }
 
+void editor_mode::infra_forget(scene::basic_node const *Node)
+{
+	Live.forget(Node);
+	auto const held = [Node](infra::binding const &Binding) { return Binding.type != infra::kind::include && Binding.node == Node; };
+	m_bindings.erase(std::remove_if(m_bindings.begin(), m_bindings.end(), held), m_bindings.end());
+	m_infra_buffer.erase(std::remove_if(m_infra_buffer.begin(), m_infra_buffer.end(), [&](infra::object_state const &State) { return held(State.saved); }), m_infra_buffer.end());
+	for (auto &candidate : m_infra.candidates)
+		if (held(candidate.binding))
+			candidate.binding.node = nullptr;
+}
+
 void editor_mode::infra_store()
 {
 	if (false == m_bindings_loaded || scene::Layers.empty())