patch 9.1.0149: null pointer member access when accessing 'winfixbuf' property

Problem:  qf_goto_win_with_qfl_file may check if prevwin has 'winfixbuf'
          set without checking if it's valid first.
Solution: Reverse the condition. Add a test, a modeline, and a missing
          CheckFeature. (Searn Dewar)

closes: #14140

Signed-off-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    149,
 /**/
     148,
 /**/