fix PrevPage and NextPage Hugo theme issue

Author: samelat

themes/poison/layouts/partials/post/navigation.html

@@ -22,14 +22,14 @@
         </ul>
     </p>
     {{ else }}
-	    {{ if .PrevPage }}
-            {{ if eq .PrevPage.Section "posts" }}
-	            <a class="previous-post" href="{{ .PrevPage.Permalink }}?ref=footer">« {{ .PrevPage.Title | truncate 50 "..."}}</a>
+	    {{ if .Prev }}
+            {{ if eq .Prev.Section "posts" }}
+	            <a class="previous-post" href="{{ .Prev.Permalink }}?ref=footer">« {{ .Prev.Title | truncate 50 "..."}}</a>
 	        {{ end }}
         {{ end }}
-	    {{ if .NextPage }}
-            {{ if eq .NextPage.Section "posts" }}
-	            <a class="next-post" href="{{ .NextPage.Permalink }}?ref=footer">{{ .NextPage.Title | truncate 50 "..." }} »</a>
+	    {{ if .Next }}
+            {{ if eq .Next.Section "posts" }}
+	            <a class="next-post" href="{{ .Next.Permalink }}?ref=footer">{{ .Next.Title | truncate 50 "..." }} »</a>
 	        {{ end }}
         {{ end }}
     {{ end }}