Protect from null param on ecpg disconnect, verified by Roland Karch

src/interfaces/ecpg/preproc/preproc.y

-/* $Header: /cvsroot/pgsql/src/interfaces/ecpg/preproc/Attic/preproc.y,v 1.204 2002/12/12 21:50:01 momjian Exp $ */
+/* $Header: /cvsroot/pgsql/src/interfaces/ecpg/preproc/Attic/preproc.y,v 1.205 2002/12/13 20:29:07 momjian Exp $ */
 
 /* Copyright comment */
 %{
@@ -554,7 +554,8 @@ stmt:  AlterDatabaseSetStmt { output_statement($1, 0, connection); }
 			if (connection)
 				mmerror(PARSE_ERROR, ET_ERROR, "no at option for disconnect statement.\n");
 
-			fprintf(yyout, "{ ECPGdisconnect(__LINE__, %s);", $1);
+			fprintf(yyout, "{ ECPGdisconnect(__LINE__, %s);",
+					$1 ? $1 : "\"CURRENT\"");
 			whenever_action(2);
 			free($1);
 		}