Move pager_read_delay check to after the blocking km_dokey()

The blocking part of the event loop of the pager is waiting for inputs
by the user.  When we check for an expired timer, we should do this
after this waiting.

Since handling the key event might alter the internal state such as the
currently selected message, we must handle the expired timer events
before the key events otherwise we might ending up operating on the
wrong message.

pager/dlg_pager.c

@@ -384,11 +384,6 @@ int mutt_pager(struct PagerView *pview)
   priv->loop = PAGER_LOOP_CONTINUE;
   do
   {
-    if (check_read_delay(&priv->delay_read_timestamp))
-    {
-      mutt_set_flag(shared->mailbox, shared->email, MUTT_READ, true);
-    }
-
     pager_queue_redraw(priv, PAGER_REDRAW_PAGER);
     notify_send(priv->notify, NT_PAGER, NT_PAGER_VIEW, priv);
     window_redraw(NULL);
@@ -522,6 +517,16 @@ int mutt_pager(struct PagerView *pview)
     // Some OP codes are not handled by pager, they cause pager to quit returning
     // OP code to index. Index handles the operation and then restarts pager
     op = km_dokey(MENU_PAGER);
+
+    // km_dokey() can block, so recheck the timer.
+    // Note: This check must occur before handling the operations of the index
+    // as those can change the currently selected message/entry yielding to
+    // marking the wrong message as read.
+    if (check_read_delay(&priv->delay_read_timestamp))
+    {
+      mutt_set_flag(shared->mailbox, shared->email, MUTT_READ, true);
+    }
+
     if (SigWinch)
       priv->pager_redraw = true;