1.
Steps to reproduce:

1. Go to Configuration -> Hosts
2. Create new "Graph" (Graph prototype, Host prototype, Discovery rule)
3. After success creation, press again "Create graph"

Result
Error message "URL parameter name is empty."
For discovery rule error in form: Undefined index: hostid [ in host_discovery.php:254]

2.
Steps to reproduce:

1. Go to Configuration -> Hosts
2. Create item/trigger/discovery rule (and other)
3. Open just created item and remove
4. After success deletion, press again "Create item"

Result
Error: No permissions to referred object or it does not exist!
Or for items: Field "itemid" must be missing.