Column utils: Missing varargs init or cleanup (CID 1212122)

Change-Id: I013c737c2cd62e3f1f49b113a7ce0c0616e1ecc4
Reviewed-on: https://code.wireshark.org/review/6119
Reviewed-by: Michael Mann <mmann78@netscape.net>

epan/column-utils.c

@@ -444,6 +444,7 @@ col_do_append_fstr(column_info *cinfo, const int el, const char *separator, cons
 
         G_VA_COPY(ap2, ap);
         g_vsnprintf(&cinfo->col_buf[i][len], (guint32)(max_len - len), format, ap2);
+        va_end(ap2);
       }
     }
   }