Report to the web view we didn't handle if the MIME type is fine

This caused blank pages to erroneously look as thought they were
loading infinitely. In fact it is due to a bug in WebKit that
this ever worked at all.

midori/midori-view.c

@@ -1160,7 +1160,7 @@ webkit_web_view_mime_type_decision_cb (GtkWidget*      web_view,
         g_strrstr (mime_type, "script") ||
         g_str_has_prefix (mime_type, "text/") || g_strrstr (mime_type, "xml"))
     #endif
-        return TRUE;
+        return FALSE;
 
     #if WEBKIT_CHECK_VERSION (1, 0, 0)
     uri = g_strdup_printf ("error:nodisplay %s",