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.

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1611,
 /**/
     1610,
 /**/