fix: handle empty input regions (#4842)

Co-authored-by: Sergio Garcia <38561120+sergargar@users.noreply.github.com>

prowler/providers/aws/aws_provider.py

@@ -78,7 +78,7 @@ class AwsProvider(Provider):
         # MFA Configuration (false by default)
         input_mfa = getattr(arguments, "mfa", None)
         input_profile = getattr(arguments, "profile", None)
-        input_regions = set(getattr(arguments, "region", set()))
+        input_regions = set(getattr(arguments, "region", []) or [])
         organizations_role_arn = getattr(arguments, "organizations_role", None)
 
         # Set if unused services must be scanned

tests/providers/aws/aws_provider_test.py

@@ -755,6 +755,14 @@ aws:
         assert aws_provider.mutelist.mutelist == mutelist["Mutelist"]
         assert aws_provider.mutelist.mutelist_file_path == dynamodb_mutelist_path
 
+    @mock_aws
+    def test_empty_input_regions_in_arguments(self):
+        arguments = Namespace()
+        arguments.region = None
+        aws_provider = AwsProvider(arguments)
+
+        assert isinstance(aws_provider, AwsProvider)
+
     @mock_aws
     def test_generate_regional_clients_all_enabled_regions(self):
         arguments = Namespace()