patch 8.2.1774: GTK: hang when forced to exit

Problem:    GTK: hang when forced to exit.
Solution:   Do not clean up "mainwin" when really_exiting is set.
            (Zdenek Dohnal, closes #7042)
diff --git a/src/version.c b/src/version.c
index acac541..5502966 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1774,
+/**/
     1773,
 /**/
     1772,