remove un-hittable error

Author: petrelharp

c/tskit/core.c

@@ -185,10 +185,6 @@ tsk_json_struct_metadata_get_blob(char *metadata, tsk_size_t metadata_length,
     }
     header_and_json_length = (uint64_t) TSK_JSON_BINARY_HEADER_SIZE + json_length_u64;
     padding_length = (8 - (header_and_json_length & 0x07)) % 8;
-    if (padding_length > UINT64_MAX - header_and_json_length) {
-        ret = tsk_trace_error(TSK_ERR_JSON_STRUCT_METADATA_INVALID_LENGTH);
-        goto out;
-    }
     header_and_json_and_padding_length = header_and_json_length + padding_length;
     if (binary_length_u64 > UINT64_MAX - header_and_json_and_padding_length) {
         ret = tsk_trace_error(TSK_ERR_JSON_STRUCT_METADATA_INVALID_LENGTH);