🐛 Fix SequenceSet#slice when length > result size

The goal is for `#[]` (aliased as `#slice`) to behave similarly to
`Array#[]`/`Array#slice`.  When `Array#slice` has a length or range that
extends beyond the end of the array, they simply return everything
up to the end.

Author: nevans

lib/net/imap/sequence_set.rb

@@ -1253,6 +1253,7 @@ def slice_range(range)
           remain_frozen_empty
         elsif (min = at(first))
           max = at(last)
+          max = :* if max.nil?
           if    max == :*  then self & (min..)
           elsif min <= max then self & (min..max)
           else                  remain_frozen_empty

test/net/imap/test_sequence_set.rb

@@ -293,6 +293,9 @@ def obj.to_sequence_set; 192_168.001_255 end
                  SequenceSet[((1..10_000) % 10).to_a][-5, 4]
     assert_nil SequenceSet[111..222, 888..999][2000, 4]
     assert_nil SequenceSet[111..222, 888..999][-2000, 4]
+    # with length longer than the remaining members
+    assert_equal SequenceSet[101...200],
+                 SequenceSet[1...200][100, 10000]
   end
 
   test "#[range]" do
@@ -319,6 +322,8 @@ def obj.to_sequence_set; 192_168.001_255 end
     assert_nil SequenceSet.empty[2..4]
     assert_nil SequenceSet[101..200][1000..1060]
     assert_nil SequenceSet[101..200][-1000..-60]
+    # with length longer than the remaining members
+    assert_equal SequenceSet[101..1111], SequenceSet[1..1111][100..999_999]
   end
 
   test "#find_index" do