fix spacing in "SASL mechanism(s) not available" error message

amends fdb03b91.

src/drv_imap.c

@@ -2174,7 +2174,7 @@ imap_open_store_authenticate2( imap_store_t *ctx )
 		free( enc );
 		return;
 	  notsasl:
-		if (!ctx->sasl || sasl_listmech( ctx->sasl, NULL, "", "", "", &saslavail, NULL, NULL ) != SASL_OK)
+		if (!ctx->sasl || sasl_listmech( ctx->sasl, NULL, "", " ", "", &saslavail, NULL, NULL ) != SASL_OK)
 			saslavail = "(none)";  /* EXTERNAL is always there anyway. */
 		if (!auth_login) {
 			error( "IMAP error: selected SASL mechanism(s) not available;\n"