Fix double map dereference indexing

src/llvm_backend_general.cpp

@@ -271,6 +271,10 @@ lbAddr lb_addr(lbValue addr) {
 
 
 lbAddr lb_addr_map(lbValue addr, lbValue map_key, Type *map_type, Type *map_result) {
+	GB_ASSERT(is_type_pointer(addr.type));
+	Type *mt = type_deref(addr.type);
+	GB_ASSERT(is_type_map(mt));
+
 	lbAddr v = {lbAddr_Map, addr};
 	v.map.key    = map_key;
 	v.map.type   = map_type;