2
could you try an if statement in the block template file? for example:
<{if $block.content}>
<div style="padding: 5px;">
<fieldset>
<legend class="blockTitle"><{$block.title}></legend>
<div class="blockContent"><{$block.content}></div>
</fieldset>
</div>
<{/if}>
?
I don't know if it would work for sure, but that would be my first shot.