Broken links displayed in upload form when creating new nodes

When creating a new node, the attachment links displayed in the upload form are broken because a node ID does not yet exist (see attached).

We should divide the hook_form_alter() into two cases: (1) creating new nodes and (2) editing old ones. In the former case, we should change the upload form help text to explain that attachment links will be visible at the bottom of the node once they save it.