Fix rare aborts in CHECK_WINDOW_END

Fix rare aborts in CHECK_WINDOW_END

Those aborts happen because a window's window_end_vpos value
is inconsistent with the current matrix's number of rows, which
happens after resizing the mini-window.
* src/xdisp.c (mark_window_display_accurate_1): Don't validate the
window_end_valid flag if window_end_vpos is inconsistent with the
current_matrix's number of rows.  This happens, e.g., when
Edebug wants to show a value in the mini-window that causes it to
resize, as the window above the mini-window was usually already
redisplayed, and we think its display is accurate.