odb: free object data when id is ambiguous

By the time we recognise this as an ambiguous id, the object's data
has been loaded into memory. Free it when returning EABMIGUOUS.

src/odb.c

@@ -786,8 +786,10 @@ attempt_lookup:
 			git__free(data);
 			data = raw.data;
 
-			if (found && git_oid__cmp(&full_oid, &found_full_oid))
+			if (found && git_oid__cmp(&full_oid, &found_full_oid)) {
+				git__free(raw.data);
 				return git_odb__error_ambiguous("multiple matches for prefix");
+			}
 
 			found_full_oid = full_oid;
 			found = true;

tests-clar/odb/mixed.c

@@ -22,6 +22,7 @@ void test_odb_mixed__dup_oid(void) {
 
 	cl_git_pass(git_oid_fromstr(&oid, hex));
 	cl_git_pass(git_odb_read_prefix(&obj, _odb, &oid, GIT_OID_HEXSZ));
+	git_odb_object_free(obj);
 	cl_git_pass(git_oid_fromstrn(&oid, short_hex, sizeof(short_hex) - 1));
 	cl_git_pass(git_odb_read_prefix(&obj, _odb, &oid, sizeof(short_hex) - 1));
 	git_odb_object_free(obj);