fixes positions.isNotEmpty errors when using route and viewportFraction

[coveralls]

Pull Request Test Coverage Report for Build 27

• 1 of 2 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 47.751%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/transformer_page_view.dart	1	2	50.0%
<!--	Total:	1	2	50.0%	-->

Totals
Change from base Build 25:	-0.2%
Covered Lines:	138
Relevant Lines:	289

---

💛 - Coveralls

[Eimji]

Thanks ! This PR must be merged !

[vmihalachi]

Please merge this PR