patch 9.0.1373: wrong text displayed when using both 'linebreak' and 'list'

Problem:    Wrong text displayed when using both 'linebreak' and 'list'.
Solution:   Only set "c_extra" to NUL when "p_extra" is not empty. (Hirohito
            Higashi, closes #12065)
diff --git a/src/version.c b/src/version.c
index bef7cf0..ede31d6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1373,
+/**/
     1372,
 /**/
     1371,