updated for version 7.4.275
Problem:    When changing the type of a sign that hasn't been placed ther is
            no error message.
Solution:   Add an error message. (Christian Brabandt)
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index f6643ae..48700f0 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -7275,7 +7275,10 @@
 	    else
 		/* ":sign place {id} file={fname}": change sign type */
 		lnum = buf_change_sign_type(buf, id, sp->sn_typenr);
-	    update_debug_sign(buf, lnum);
+	    if (lnum > 0)
+		update_debug_sign(buf, lnum);
+	    else
+		EMSG2(_("E885: Not possible to change sign %s"), sign_name);
 	}
 	else
 	    EMSG(_(e_invarg));