Fix forms.destroyall() and call it when lua console closes

Fixes #454

BizHawk.Client.EmuHawk/tools/Lua/Libraries/EmuLuaLibrary.Forms.cs

@@ -190,10 +190,9 @@ namespace BizHawk.Client.EmuHawk
 		)]
 		public void DestroyAll()
 		{
-			foreach (var form in _luaForms)
+			for (var i = _luaForms.Count - 1; i >= 0; i--)
 			{
-				form.Close();
+				_luaForms.ElementAt(i).Close();
-				_luaForms.Remove(form);
 			}
 		}
 

BizHawk.Client.EmuHawk/tools/Lua/Libraries/EmuLuaLibrary.cs

@@ -136,6 +136,7 @@ namespace BizHawk.Client.EmuHawk
 
 		public void Close()
 		{
+			FormsLibrary.DestroyAll();
 			_lua = new Lua();
 			GuiLibrary.Dispose();
 		}