Don't error when checking patch.valid on invalid patches

src/lua_hudlib.c

@@ -268,10 +268,14 @@ static int patch_get(lua_State *L)
 #endif
 	enum patch field = luaL_checkoption(L, 2, NULL, patch_opt);
 
-	// patches are CURRENTLY always valid, expected to be cached with PU_STATIC
-	// this may change in the future, so patch.valid still exists
-	if (!patch)
+	// patches are invalidated when switching renderers
+	if (!patch) {
+		if (field == patch_valid) {
+			lua_pushboolean(L, 0);
+			return 1;
+		}
 		return LUA_ErrInvalid(L, "patch_t");
+	}
 
 	switch (field)
 	{