I have a weblog entries tag (ee 1.7.0) that ignores anything inside the weblog:entries tags if there’s no entry for category.
If an entry does exist, everything outputs fine. I am passing the values with an embed (if that matters), but I did try hardcoding the values to test and that didn’t make a difference.
{exp:weblog:entries weblog="{embed:my_weblog}" dynamic="off" category="{embed:my_category}"}
{if no_results}Content to come.{/if}...{/exp:weblog:entries}