indexer: check return code of git_hash_ctx_init

Initialization of the hashing context may fail on some systems, most
notably on Win32 via the legacy hashing context. As such, we need to
always check the error code of `git_hash_ctx_init`, which is not done
when creating a new indexer.

Fix the issue by adding checks.

Author: pks-t

src/indexer.c

@@ -150,11 +150,11 @@ int git_indexer_new(
 	idx->progress_cb = opts.progress_cb;
 	idx->progress_payload = opts.progress_cb_payload;
 	idx->mode = mode ? mode : GIT_PACK_FILE_MODE;
-	git_hash_ctx_init(&idx->hash_ctx);
-	git_hash_ctx_init(&idx->trailer);
 	git_buf_init(&idx->entry_data, 0);
 
-	if ((error = git_oidmap_new(&idx->expected_oids)) < 0)
+	if ((error = git_hash_ctx_init(&idx->hash_ctx)) < 0 ||
+	    (error = git_hash_ctx_init(&idx->trailer)) < 0 ||
+	    (error = git_oidmap_new(&idx->expected_oids)) < 0)
 		goto cleanup;
 
 	idx->do_verify = opts.verify;