Fix regression when stubbed method invoked with no args

In this commit [1] which was part of #660 and was released in v2.4.3,
the new code didn't take into account that the `parameter` local
variable in `HasEntries#matches?` can be `nil` if the stubbed method
expects a `Hash` or keyword arguments but is called with no arguments.

Previously this wasn't a problem, because the `nil` was handled by this
guard condition [2] in `HasEntry#matches?`. However, now we're calling
`#length` on `parameter` when `exact` is `true`, we need this new guard
condition in `HasEntries#matches?`.

[1]: 5e6a07b
[2]: https://github.com/freerange/mocha/blob/e95fda25c41faaa4a7737b62a471544c5c2ddf2f/lib/mocha/parameter_matchers/has_entry.rb#L68

lib/mocha/parameter_matchers/has_entries.rb

@@ -38,6 +38,7 @@ def initialize(entries, exact: false)
       # @private
       def matches?(available_parameters)
         parameter = available_parameters.shift
+        return false unless parameter
         return false if @exact && @entries.length != parameter.length
 
         has_entry_matchers = @entries.map { |key, value| HasEntry.new(key, value) }

test/acceptance/parameter_matcher_test.rb

@@ -29,6 +29,15 @@ def test_should_not_match_hash_parameter_which_is_not_exactly_the_same
     assert_failed(test_result)
   end
 
+  def test_should_not_match_hash_parameter_when_method_invoked_with_no_parameters
+    test_result = run_as_test do
+      mock = mock()
+      mock.expects(:method).with(key_1: 'value_1')
+      mock.method
+    end
+    assert_failed(test_result)
+  end
+
   def test_should_match_hash_parameter_with_specified_key
     test_result = run_as_test do
       mock = mock()

test/unit/parameter_matchers/has_entries_test.rb

@@ -17,6 +17,16 @@ def test_should_not_match_hash_not_including_specified_entries
     assert !matcher.matches?([{ key_1: 'value_1', key_2: 'value_2' }])
   end
 
+  def test_should_not_match_no_arguments_when_exact_match_not_required
+    matcher = has_entries(key_1: 'value_1')
+    assert !matcher.matches?([nil])
+  end
+
+  def test_should_not_match_no_arguments_when_exact_match_required
+    matcher = HasEntries.new({ key_1: 'value_1' }, exact: true)
+    assert !matcher.matches?([nil])
+  end
+
   def test_should_describe_matcher
     matcher = has_entries(key_1: 'value_1', key_2: 'value_2')
     description = matcher.mocha_inspect