Use the lineno attribute of TextNode.token if TextNode.position is unavailable

[TaylorSMarks]

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This fixed an issue I had in one of my files. I have no idea whether the TextNode was lacking a position because of a bug within Django or in my code, or if this was to be expected and Django_Coverage_Plugin needs to handle this.

I don't have a test case that I can publicly share, but I can say that without my change, it wasn't properly seeing that the file was being used, and with this change, it worked fine.