Fixed undefined behaviour when love exceptions are converted into Lua errors (resolves issue #729)

src/modules/physics/box2d/wrap_Fixture.cpp

@@ -65,7 +65,7 @@ int w_Fixture_setDensity(lua_State *L)
 {
 	Fixture *t = luax_checkfixture(L, 1);
 	float arg1 = (float)luaL_checknumber(L, 2);
-	ASSERT_GUARD(t->setDensity(arg1);)
+	EXCEPT_GUARD(t->setDensity(arg1);)
 	return 0;
 }
 
@@ -156,7 +156,9 @@ int w_Fixture_rayCast(lua_State *L)
 {
 	Fixture *t = luax_checkfixture(L, 1);
 	lua_remove(L, 1);
-	ASSERT_GUARD(return t->rayCast(L);)
+	int ret = 0;
+	EXCEPT_GUARD(ret = t->rayCast(L);)
+	return ret;
 }
 
 int w_Fixture_setFilterData(lua_State *L)
@@ -256,14 +258,7 @@ int w_Fixture_setGroupIndex(lua_State *L)
 int w_Fixture_destroy(lua_State *L)
 {
 	Fixture *t = luax_checkfixture(L, 1);
-	try
-	{
-		t->destroy();
-	}
-	catch(love::Exception &e)
-	{
-		luaL_error(L, "%s", e.what());
-	}
+	EXCEPT_GUARD(t->destroy();)
 	return 0;
 }