[spec] close iterator if abrupt during StepValue

Author: ljharb

spec.emu

@@ -23,7 +23,9 @@ copyright: false
     1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_ and _chunkSize_ and performs the following steps when called:
       1. Let _buffer_ be a new empty List.
       1. Repeat,
-        1. Let _value_ be ? IteratorStepValue(_iterated_).
+        1. Let _result_ be Completion(IteratorStepValue(_iterated_)).
+        1. IfAbruptCloseIterator(_result_, _iterated_).
+        1. Let _value_ be ! _result_.
         1. If _value_ is ~done~, then
           1. If _buffer_ is not empty, then
             1. Perform Completion(Yield(CreateArrayFromList(_buffer_))).
@@ -57,7 +59,9 @@ copyright: false
     1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_, _windowSize_, and _undersized_ and performs the following steps when called:
       1. Let _buffer_ be a new empty List.
       1. Repeat,
-        1. Let _value_ be ? IteratorStepValue(_iterated_).
+        1. Let _result_ be Completion(IteratorStepValue(_iterated_)).
+        1. IfAbruptCloseIterator(_result_, _iterated_).
+        1. Let _value_ be ! _result_.
         1. If _value_ is ~done~, then
           1. If _undersized_ is *"allow-partial"*, _buffer_ is not empty, and the number of elements in _buffer_ < ℝ(_windowSize_), then
             1. Perform Completion(Yield(CreateArrayFromList(_buffer_))).