Weird MVEL issue

gistfile1.java

// This works:
discount = 50.0
if (!doc["discount"].empty) { 
  discount = doc["discount"].value; 
} else { 
  discount = 50.0;
}

// This works:
discount = doc["discount"].empty ? 50.0 : doc["discount"].value;

// This doesn't
discount = 50.0
if (!doc["discount"].empty) { 
  discount = doc["discount"].value; 
}