[GSS] (7.10.x) RHS doesn't have a type

As a follow-up to RHDM-1754, we have a case with the following rule snippet: 
 
    $s2Latest: ParticipantEvent() from accumulate(
        $t2: ParticipantEvent(
            this != $t1,
            this meets[2h] $t1,
            location == "JEWELLERY_STORE"),
        init(Collector c = new Collector(); c.pEvent = null,
        action( if(null == c.pEvent)

{                     c.pEvent = $t2;                 }

                else{
                    if($t2.getRegisteredTime() > c.pEvent.getRegisteredTime())

{                         c.pEvent = $t2;                     }

                }
             ),
        reverse(),
        result(c.pEvent)
        )
 
Collector is just a POJO with a pEvent variable.
 
Compiling this with the executable model fails with:
 
Caused by: org.drools.mvelcompiler.MvelCompilerException: RHS doesn't have a type
    at org.drools.mvelcompiler.LHSPhase.lambda$getRHSType$20 (LHSPhase.java:371)
    at java.util.Optional.orElseThrow (Optional.java:408)
    at org.drools.mvelcompiler.LHSPhase.getRHSType (LHSPhase.java:371)
    at org.drools.mvelcompiler.LHSPhase.lambda$visit$3 (LHSPhase.java:125)

 
How can the return type be defined here? Reproducer project attached.