If you just want the link to disappear completely, just use an 'if' around the link_to, rather than link_to_if.
<% if condition %>
<%= link_to ... %>
<% end %>
If you want something else to appear when the condition is not true, you can pass a block to render instead. Having said that, from a stylistic perspective, I think I prefer 'if' 'else' to the block syntax - it's less confusing, at least to my eye.
Block syntax:
<%= link_to_if(condition, "Link Title", dest ) { link_to( "Alt Title", alt_dest ) } %>
If/else syntax:
<% if condition %>
<%= link_to "Link Title", dest %>
<% else %>
<%= link_to "Alt Title", alt_dest %>
<% end >
For more information see the documentation for UrlHelper.