Remove unneeded is_empty check

Signed-off-by: Moritz Hoffmann <[email protected]>

Author: antiguru

timely/src/dataflow/operators/core/filter.rs

@@ -30,9 +30,7 @@ where
     fn filter<P: FnMut(&C::Item<'_>)->bool+'static>(&self, mut predicate: P) -> StreamCore<G, C> {
         self.unary(Pipeline, "Filter", move |_,_| move |input, output| {
             input.for_each(|time, data| {
-                if !data.is_empty() {
-                    output.session(&time).give_iterator(data.drain().filter(&mut predicate));
-                }
+                output.session(&time).give_iterator(data.drain().filter(&mut predicate));
             });
         })
     }