Slightly better error message when get_chain() returns something bogus.

diff --git a/theme.cpp b/theme.cpp
index a5f8cfbba6c1d38e3b1cd0a4514567323ad4f239..1d0cd2d643db006a4fae075f8aed7c817e5e176f 100644 (file)
--- a/theme.cpp
+++ b/theme.cpp
@@ -761,7 +761,12 @@ Theme::Chain Theme::get_chain(unsigned num, float t, unsigned width, unsigned he
                exit(1);
        }
 
-       chain.chain = (EffectChain *)luaL_checkudata(L, -2, "EffectChain");
+       chain.chain = (EffectChain *)luaL_testudata(L, -2, "EffectChain");
+       if (chain.chain == nullptr) {
+               fprintf(stderr, "get_chain() for chain number %d did not return an EffectChain\n",
+                       num);
+               exit(1);
+       }
        if (!lua_isfunction(L, -1)) {
                fprintf(stderr, "Argument #-1 should be a function\n");
                exit(1);