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>
diff --git a/src/version.c b/src/version.c
index cecf089..46781f0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    149,
+/**/
     148,
 /**/
     147,