Steps to reproduce:

1. Create template "A" with discovery rule.
2. Create template "B" which links template "A".
3. Create host "test" which uses template "B".
4. Open discovery rule in "B" template settings and press "Update".

Result:

 

• Undefined index: type [host_discovery.php:324 → CApiWrapper->__call() → CFrontendApiWrapper->callMethod() → CApiWrapper->callMethod() → CFrontendApiWrapper->callClientMethod() → CLocalApiClient->callMethod() → CDiscoveryRule->update() → CDiscoveryRule->inherit() → CItemGeneral->prepareInheritedItems() in include/classes/api/services/CItemGeneral.php:1029]
• Undefined index: type [host_discovery.php:324 → CApiWrapper->__call() → CFrontendApiWrapper->callMethod() → CApiWrapper->callMethod() → CFrontendApiWrapper->callClientMethod() → CLocalApiClient->callMethod() → CDiscoveryRule->update() → CDiscoveryRule->inherit() → CItemGeneral->prepareInheritedItems() in include/classes/api/services/CItemGeneral.php:1030]
• array_key_exists(): The first argument should be either a string or an integer [host_discovery.php:324 → CApiWrapper->__call() → CFrontendApiWrapper->callMethod() → CApiWrapper->callMethod() → CFrontendApiWrapper->callClientMethod() → CLocalApiClient->callMethod() → CDiscoveryRule->update() → CDiscoveryRule->inherit() → CItemGeneral->prepareInheritedItems() → CItemGeneral::findInterfaceForItem() → array_key_exists() in include/classes/api/services/CItemGeneral.php:701]
• Cannot find host interface on "test" for item key "custom.vfs.fs.discovery".

Expected:
no errors and successful update of all allowed values (interval or filters)