sieve-tools: Terminate with a fatal error when script cannot be compi…

…led/opened.

Rather than continuing with binary == NULL, causing a segfault.

src/lib-sieve-tool/sieve-tool.c

@@ -536,7 +536,7 @@ struct sieve_binary *sieve_tool_script_compile
 
 	if ( (sbin = sieve_compile
 		(svinst, filename, name, ehandler, 0, NULL)) == NULL )
-		i_error("failed to compile sieve script '%s'", filename);
+		i_fatal("failed to compile sieve script '%s'", filename);
 
 	sieve_error_handler_unref(&ehandler);