patch 8.2.3446: not enough tests for empty string arguments

Problem:    Not enough tests for empty string arguments.
Solution:   Add tests, fix type check. (Yegappan Lakshmanan, closes #8881)
diff --git a/src/version.c b/src/version.c
index 6c2e4d1..21a697d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3446,
+/**/
     3445,
 /**/
     3444,