patch 8.0.1276: key lost when window closed in exit callback

Problem:    Typed key is lost when the terminal window is closed in exit
            callback. (Gabriel Barta)
Solution:   When the current window changes bail out of the wait loop. (closes
            #2302)
diff --git a/src/version.c b/src/version.c
index abac386..39bad6c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1276,
+/**/
     1275,
 /**/
     1274,