patch 8.1.1611: bufadd() reuses existing buffer without a name

Problem:    Bufadd() reuses existing buffer without a name.
Solution:   When the name is empty always create a new buffer.
diff --git a/src/version.c b/src/version.c
index 6fce98b..a1c5f88 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1611,
+/**/
     1610,
 /**/
     1609,