Steps to reproduce:

1. Create an Item on a Linux host that monitors a log file, using a regex: logrt[/var/log/syslog,"(?i)error:"]
2. Create a trigger using the following expression: length(last(/hostname.com/logrt[/var/log/syslog,"(?i)error:"]))>=1
3. Using the Expression Constructor, test the expression.  Note that when text is entered in the box it returns true, when text is removed from the box it returns false.
4. Save the trigger with the expression.
5. Note the error that is shown "Cannot convert expression result of type "string" to floating point value"

Result:
The trigger is saved/updated, but shows an error "Cannot convert expression result of type "string" to floating point value"
Trigger does not work and cannot be used.
Expected:
I expected that length would return a number that that is either 0, or the number of characters in {{last(/hostname.com/logrt[/var/log/syslog,"(?i)error:"]) }}and be triggerable on this.