Merged r9759 to r9764.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.0-stable@9766 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/views/issues/show.html.erb

@@ -7,14 +7,14 @@
     <div class="next-prev-links contextual">
       <%= link_to_if @prev_issue_id,
                      "\xc2\xab #{l(:label_previous)}",
-                     issue_path(@prev_issue_id),
+                     (@prev_issue_id ? issue_path(@prev_issue_id) : nil),
                      :title => "##{@prev_issue_id}" %> |
       <% if @issue_position && @issue_count %>
         <span class="position"><%= l(:label_item_position, :position => @issue_position, :count => @issue_count) %></span> |
       <% end %>
       <%= link_to_if @next_issue_id,
                      "#{l(:label_next)} \xc2\xbb",
-                     issue_path(@next_issue_id),
+                     (@next_issue_id ? issue_path(@next_issue_id) : nil),
                      :title => "##{@next_issue_id}" %>
     </div>
   <% end %>