efi_loader: check parameter in InstallConfigurationTable

Check that parameter guid is not NULL. This avoids a possible NULL
pointer exception.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_loader/efi_boottime.c

@@ -1333,6 +1333,9 @@ efi_status_t efi_install_configuration_table(const efi_guid_t *guid, void *table
 {
 	int i;
 
+	if (!guid)
+		return EFI_INVALID_PARAMETER;
+
 	/* Check for guid override */
 	for (i = 0; i < systab.nr_tables; i++) {
 		if (!guidcmp(guid, &efi_conf_table[i].guid)) {