index: assert required OID are non-NULL

src/index.c

@@ -963,14 +963,20 @@ static int index_entry_reuc_init(git_index_reuc_entry **reuc_out,
 	*reuc_out = reuc = reuc_entry_alloc(path);
 	GITERR_CHECK_ALLOC(reuc);
 
-	if ((reuc->mode[0] = ancestor_mode) > 0)
+	if ((reuc->mode[0] = ancestor_mode) > 0) {
+		assert(ancestor_oid);
 		git_oid_cpy(&reuc->oid[0], ancestor_oid);
+	}
 
-	if ((reuc->mode[1] = our_mode) > 0)
+	if ((reuc->mode[1] = our_mode) > 0) {
+		assert(our_oid);
 		git_oid_cpy(&reuc->oid[1], our_oid);
+	}
 
-	if ((reuc->mode[2] = their_mode) > 0)
+	if ((reuc->mode[2] = their_mode) > 0) {
+		assert(their_oid);
 		git_oid_cpy(&reuc->oid[2], their_oid);
+	}
 
 	return 0;
 }