Fix logic for showing sign up link

This prevents the link from showing when an instance lands on the sign
up page anyway.

Ref T681

templates/base.tmpl

@@ -47,7 +47,7 @@
 					{{if not .DisableDrafts}}<a href="/me/posts/"{{if eq .Path "/me/posts/"}} class="selected"{{end}}>Drafts</a>{{end}}
 						{{ end }}
 					{{if and (and  .LocalTimeline .CanViewReader) (not .Chorus)}}<a href="/read"{{if eq .Path "/read"}} class="selected"{{end}}>Reader</a>{{end}}
-					{{if and (and  .Chorus .OpenRegistration) (not .Username)}}<a href="/signup"{{if eq .Path "/signup"}} class="selected"{{end}}>Sign up</a>{{end}}
+					{{if and (and (and  .Chorus .OpenRegistration) (not .Username)) (or (not .Private) (ne .Landing ""))}}<a href="/signup"{{if eq .Path "/signup"}} class="selected"{{end}}>Sign up</a>{{end}}
 					{{if not .Username}}<a href="/login"{{if eq .Path "/login"}} class="selected"{{end}}>Log in</a>{{else if .SimpleNav}}<a href="/me/logout">Log out</a>{{end}}
 					{{ end }}
 				</nav>

templates/user/include/header.tmpl

@@ -56,7 +56,7 @@
 					{{if not .DisableDrafts}}<a href="/me/posts/"{{if eq .Path "/me/posts/"}} class="selected"{{end}}>Drafts</a>{{end}}
 						{{ end }}
 					{{if and (and .LocalTimeline .CanViewReader) (not .Chorus)}}<a href="/read">Reader</a>{{end}}
-					{{if and (and .Chorus .OpenRegistration) (not .Username)}}<a href="/signup"{{if eq .Path "/signup"}} class="selected"{{end}}>Sign up</a>{{end}}
+					{{if and (and (and .Chorus .OpenRegistration) (not .Username)) (or (not .Private) (ne .Landing ""))}}<a href="/signup"{{if eq .Path "/signup"}} class="selected"{{end}}>Sign up</a>{{end}}
 					{{if .Username}}<a href="/me/logout">Log out</a>{{else}}<a href="/login">Log in</a>{{end}}
 					{{ end }}
 				{{else}}