Fix crash on script load errors

src/auto4_lua.cpp

@@ -61,6 +61,7 @@
 #include <boost/algorithm/string/case_conv.hpp>
 #include <boost/algorithm/string/classification.hpp>
 #include <boost/format.hpp>
+#include <boost/scope_exit.hpp>
 #include <cassert>
 #include <cstdint>
 #include <lauxlib.h>
@@ -373,9 +374,13 @@ namespace {
 	{
 		Destroy();
 
-		try {
+		name = GetPrettyFilename().string();
+
 		// create lua environment
 		L = lua_open();
+
+		bool loaded = false;
+		BOOST_SCOPE_EXIT_ALL(&) { if (!loaded) Destroy(); };
 		LuaStackcheck stackcheck(L);
 
 		// register standard libs
@@ -431,9 +436,9 @@ namespace {
 
 		// load user script
 		if (!LoadFile(L, GetFilename())) {
-				std::string err = get_string_or_default(L, 1);
+			description = get_string_or_default(L, 1);
 			lua_pop(L, 1);
-				throw ScriptLoadError(err);
+			return;
 		}
 		stackcheck.check_stack(1);
 
@@ -442,16 +447,17 @@ namespace {
 		// don't thread this, as there's no point in it and it seems to break on wx 2.8.3, for some reason
 		if (lua_pcall(L, 0, 0, 0)) {
 			// error occurred, assumed to be on top of Lua stack
-				std::string err = str(boost::format("Error initialising Lua script \"%s\":\n\n%s") % GetPrettyFilename().string() % get_string_or_default(L, -1));
+			description = str(boost::format("Error initialising Lua script \"%s\":\n\n%s") % GetPrettyFilename().string() % get_string_or_default(L, -1));
 			lua_pop(L, 1);
-				throw ScriptLoadError(err);
+			return;
 		}
 		stackcheck.check_stack(0);
 
 		lua_getglobal(L, "version");
 		if (lua_isnumber(L, -1) && lua_tointeger(L, -1) == 3) {
 			lua_pop(L, 1); // just to avoid tripping the stackcheck in debug
-				throw ScriptLoadError("Attempted to load an Automation 3 script as an Automation 4 Lua script. Automation 3 is no longer supported.");
+			description = "Attempted to load an Automation 3 script as an Automation 4 Lua script. Automation 3 is no longer supported.";
+			return;
 		}
 
 		name = get_global_string(L, "script_name");
@@ -464,14 +470,7 @@ namespace {
 
 		lua_pop(L, 1);
 		// if we got this far, the script should be ready
-			stackcheck.check_stack(0);
-
-		}
-		catch (agi::Exception const& e) {
-			Destroy();
-			name = GetPrettyFilename().string();
-			description = e.GetChainedMessage();
-		}
+		loaded = true;
 	}
 
 	void LuaScript::Destroy()

src/auto4_lua_progresssink.cpp

@@ -173,7 +173,7 @@ namespace Automation4 {
 				luaL_where(L, 1);
 				lua_insert(L, 1);
 				lua_concat(L, 2);
-				throw error_tag();
+				lua_error(L);
 			}
 		}