patch 7.4.2225
Problem:    Crash when placing a sign in a deleted buffer.
Solution:   Check for missing buffer name. (Dominique Pelle). Add a test.
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index aeb2bf9..919aafc 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -7861,6 +7861,11 @@
 		{			/* ... not currently in a window */
 		    char_u	*cmd;
 
+		    if (buf->b_fname == NULL)
+		    {
+			EMSG(_("E934: Cannot jump to a buffer that does not have a name"));
+			return;
+		    }
 		    cmd = alloc((unsigned)STRLEN(buf->b_fname) + 25);
 		    if (cmd == NULL)
 			return;