patch 9.1.0458: Coverity complains about division by zero

Problem:  Coverity complains about division by zero
Solution: Check explicitly for sw_val being zero

Shouldn't happen, since tabstop value should always be larger than zero.
So just add this as a safety measure.

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 221fcf8..068c079 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    458,
+/**/
     457,
 /**/
     456,