* window.c (Fprevious_window): Use FRAME_HAS_MINIBUF_P to decide

	if the frame has a minibuffer; FRAME_MINIBUF_WINDOW points to the
	surrogate on minibufferless frames, not nil.

src/window.c

@@ -978,8 +978,9 @@ windows, eventually ending up back at the window you started with.\n\
 #endif
 	    /* If this frame has a minibuffer, find that window first,
 	       because it is conceptually the last window in that frame.  */
-	    tem = FRAME_MINIBUF_WINDOW (XFRAME (tem));
-	    if (NILP (tem))
+	    if (FRAME_HAS_MINIBUF_P (XFRAME (tem)))
+	      tem = FRAME_MINIBUF_WINDOW (XFRAME (tem));
+	    else
 	      tem = FRAME_ROOT_WINDOW (XFRAME (tem));
 
 	    break;