fix for edge case if DD has no file node

[mfshao]

Link to JIRA ticket if there is one:

New Features

Breaking Changes

Bug Fixes

Improvements

• don't generate explorerPageQuery for GQL if there is no file nodes in data dict

Dependency updates

Deployment changes

[github-actions]

filepath	passed	failed	skipped	SUBTOTAL
tests/test_gen3ff_landing_page.py	0	0	2	2
tests/test_discoverypage.py	0	0	1	1
tests/test_requestor.py	5	0	0	5
tests/test_data_upload.py	2	0	0	2
tests/test_graph_submit_and_query.py	1	0	0	1
tests/test_homepage.py	1	0	0	1
tests/test_login_page.py	2	0	0	2
tests/test_register_user.py	2	0	0	2
tests/test_audit_service.py	1	0	0	1
tests/test_ras_authn.py	1	2	0	3
tests/test_pfb_export.py	0	1	0	1
TOTAL	15	3	3	21

Please find the detailed integration test report here (login here first)

[github-actions]

filepath	failed	SUBTOTAL
tests/test_pfb_export.py	1	1
TOTAL	1	1

Please find the detailed integration test report here (login here first)

[github-actions]

filepath	failed	SUBTOTAL
tests/test_pfb_export.py	1	1
TOTAL	1	1

Please find the detailed integration test report here (login here first)

[github-actions]

filepath	failed	SUBTOTAL
tests/test_pfb_export.py	1	1
TOTAL	1	1

Please find the detailed integration test report here (login here first)

[github-actions]

filepath	passed	skipped	SUBTOTAL
tests/test_gen3ff_landing_page.py	0	2	2
tests/test_ras_authn.py	0	3	3
tests/test_requestor.py	5	0	5
tests/test_register_user.py	2	0	2
tests/test_data_upload.py	2	0	2
tests/test_graph_submit_and_query.py	1	0	1
tests/test_homepage.py	1	0	1
tests/test_login_page.py	2	0	2
tests/test_audit_service.py	1	0	1
tests/test_discoverypage.py	1	0	1
tests/test_pfb_export.py	1	0	1
TOTAL	16	5	21

Please find the detailed integration test report here (login here first)