submodule.c: report the submodule that an error occurs in

diff --git a/split-index.c b/split-index.c
index 83e39ec8d7739816188ba909a4cb9da302d48f73..284d04d67f885d8905130e138c45cc4ff4fbdc30 100644 (file)
--- a/split-index.c
+++ b/split-index.c
@@ -238,6 +238,8 @@ void prepare_to_write_split_index(struct index_state *istate)
                                ALLOC_GROW(entries, nr_entries+1, nr_alloc);
                                entries[nr_entries++] = ce;
                        }
+                       if (is_null_oid(&ce->oid))
+                               istate->drop_cache_tree = 1;
                }
        }