patch 8.1.1312: Coverity warning for using uninitialized variable

Problem:    Coverity warning for using uninitialized variable.
Solution:   Clear exarg_T.
diff --git a/src/version.c b/src/version.c
index a9b376e..2b936d7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1312,
+/**/
     1311,
 /**/
     1310,