You could workaround this issue using CSS, if you want a solution that will work immediately.

For example:

[[span class="website%%form_data{link}%%"]] [%%form_data{link}%% Website] [[/span]]

[[module CSS]]
.website {
    display: none;
}
[[/module]]

For the CSS you can use either the CSS module, as I have done in the example, or add it to your existing theme.

When there is no website, the CSS class associated with that span element is 'website'. Therefore, because of the CSS rule we put in place, everything between the span tags is hidden when there is no website.

If a website URL was entered, the class would be something like 'websitehttp…' instead, which means that it is not affected by the CSS rule and the link is left visible.

I respectfully disagree that the workaround is ugly. While it does require coding that might be a little tougher to read, it really does work well. I have been using this technique for quite some time to hide empty data form fields. I take a more generic approach and name my classes something easy to remember that defines their purpose and use it like leiger described on both block and inline elements. Expanding on what leiger described, if I want to display conditional content if the form field is empty, I use the technique below. I have a form that can have 0, 1 or 2 image links on the form. If both images are absent, then I display a message indicating that. I use the .showme-inline class for conditionally displaying inline elements.

CSS

.hideme {
    display: none;
}
.showme {
    display: block;
}
.showme-inline {
    display: inline;
}

Sample to conditionally display data

This code is part of my form _template page. I use this form for an equipment inventory list that can have images attached showing the piece of equipment and/or its location.

++ Related Images
[!-- Hide this div block by default. if both form fields are empty, then display it. --] 
[[div class="hideme showme%%form_data{locationpic}%%%%form_data{detailpic}%%%%form_data{altdetailpic}%%"]]
> No images are linked to this item.
[[/div]]
[!-- Hide this image only if the form field is empty --]
[[div class="hideme%%form_data{locationpic}%%"]]
[[include :snippets:image
|image=%%form_data{locationpic}%%
|link=*/local--files%%form_data{locationpic}%%
|width=150px
|float=left
|caption=Location Image
]]
[[/div]]
[!-- Hide this image only if the form field is empty --]
[[div class="hideme%%form_data{detailpic}%%"]]
[[include :snippets:image
|image=%%form_data{detailpic}%%
|link=*/local--files%%form_data{detailpic}%%
|width=150px
|float=left
|caption=Detail Image
]]
[[/div]]
[[/div]]

I realize that this method doesn't relate specifically to ListPages, but in both cases it's a one-time "set it and forget it" task (unless you change the form or how you want to display the data).

Also, how would propose that the syntax in ListPages would work? It seems that it could get a bit messy trying to work that out as well.

This may be a discussion better suited for the community forum.