MVELExprAnalyzer assesses a correct date syntax as error

Description of problem:
Although a following drl works fine, there is an ERROR report in Problem tab.

[rule]
rule "GoodBye"
when
Message( status == Message.GOODBYE, myMessage : message, today <= "2015/07/26" )
then
System.out.println( myMessage );
end

[error message]
Unable to Analyse Expression today <= "2015/07/26":
[Error: Comparison operation requires compatible types. Found class java.util.Date and class java.lang.String]
[Near :

]
^

Version-Release number of selected component (if applicable):
JBDS 8.1.0.GA
JBDSIS 8.0.2.GA

Steps to Reproduce:
1. Create a new sample Drools project using JBDS
2. Replace a drl file with the attached one
3. check problem tab(make sure the Drools runtime is set)

Actual results:
There is a error message relating with the rule

Expected results:
There is no error message

Additional info: