patch 9.1.1650: popup: window may not properly resize

Problem:  After scrolling a popup and then using popup_settext() with
          fewer lines, the popup fails to resize properly because
          firstline points beyond the new buffer content (lifepillar)
Solution: In popup_adjust_position(), validate that firstline doesn't
          exceed buffer line count and reset to 0 (auto-position) if it
          does (glepnir)

fixes: #14745
closes: #18031

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1650,
 /**/
     1649,
 /**/