Index: trac/trac/ticket/report.py
===================================================================
--- trac/trac/ticket/report.py	(revision 6891)
+++ trac/trac/ticket/report.py	(working copy)
@@ -412,7 +412,7 @@
                      'sorting_enabled': len(row_groups)==1,
                      'email_map': email_map})
 
-        if id:
+        if id and id != -1:
             self.add_alternate_links(req, args)
 
         if format == 'rss':
Index: trac/trac/wiki/web_ui.py
===================================================================
--- trac/trac/wiki/web_ui.py	(revision 6891)
+++ trac/trac/wiki/web_ui.py	(working copy)
@@ -448,15 +448,16 @@
         version = page.resource.version
 
         # Add registered converters
-        for conversion in Mimeview(self.env).get_supported_conversions(
-                                             'text/x-trac-wiki'):
-            conversion_href = req.href.wiki(page.name, version=version,
-                                            format=conversion[0])
-            # or...
-            conversion_href = get_resource_url(self.env, page.resource,
-                                               req.href, format=conversion[0])
-            add_link(req, 'alternate', conversion_href, conversion[1],
-                     conversion[3])
+        if page.exists:
+            for conversion in Mimeview(self.env).get_supported_conversions(
+                                                 'text/x-trac-wiki'):
+                conversion_href = req.href.wiki(page.name, version=version,
+                                                format=conversion[0])
+                # or...
+                conversion_href = get_resource_url(self.env, page.resource,
+                                                req.href, format=conversion[0])
+                add_link(req, 'alternate', conversion_href, conversion[1],
+                         conversion[3])
 
         data = self._page_data(req, page)
         if page.name == 'WikiStart':