show no of txpool if not zero only

src/templates/mempool_error.html

@@ -5,7 +5,8 @@
 <div class="center info" style="text-align: center;width:80%;color:#949490">
     
    <p>Mempool data preparation for the front page failed.
-    Its processing {{#network_info}}({{tx_pool_size}} txs){{/network_info}}
+    Its processing
+       {{#network_info}}{{#tx_pool_size}}({{tx_pool_size}} txs){{/tx_pool_size}}{{/network_info}}
        took longer than expected and it timed out.
     To view mempool without time constrain,
     go to dedicated mempool page: <a href="/mempool">memory pool</a>