patch 8.1.0755: error message for get() on a Blob with invalid index

Problem:    Error message for get() on a Blob with invalid index.
Solution:   Return an empty Blob, like get() on a List does.
diff --git a/src/version.c b/src/version.c
index cf58605..bb13765 100644
--- a/src/version.c
+++ b/src/version.c
@@ -796,6 +796,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    755,
+/**/
     754,
 /**/
     753,