Account for blank pagedata

[sternj]

I received the following error:

github.com/juruen/rmapi/archive.(*Zip).readPagedata(0xc00035e800, 0xc0001800f8?)
	/home/runner/work/rmapi/rmapi/archive/reader.go:144 +0x2fd
github.com/juruen/rmapi/archive.(*Zip).Read(0xc00035e800, {0x168cfe0?, 0xc0001800f8?}, 0xc0003314b8?)
	/home/runner/work/rmapi/rmapi/archive/reader.go:47 +0xa5
github.com/juruen/rmapi/annotations.(*PdfGenerator).Generate(0xc0003319b8)
	/home/runner/work/rmapi/rmapi/annotations/pdf.go:64 +0xf6
github.com/juruen/rmapi/shell.getACmd.func1(0xc00018a750)
	/home/runner/work/rmapi/rmapi/shell/geta.go:57 +0x6ae
github.com/abiosoft/ishell.(*Shell).handleCommand(0xc0002240f0, {0xc00031ab60, 0x2, 0x2})
	/home/runner/go/pkg/mod/github.com/abiosoft/ishell@v2.0.0+incompatible/ishell.go:250 +0xec
github.com/abiosoft/ishell.handleInput(0xc0002240f0, {0xc00031ab60, 0x2, 0x2})
	/home/runner/go/pkg/mod/github.com/abiosoft/ishell@v2.0.0+incompatible/ishell.go:204 +0x31
github.com/abiosoft/ishell.(*Shell).run(0xc0002240f0)
	/home/runner/go/pkg/mod/github.com/abiosoft/ishell@v2.0.0+incompatible/ishell.go:183 +0x2ef
github.com/abiosoft/ishell.(*Shell).Run(0xc000370000?)
	/home/runner/go/pkg/mod/github.com/abiosoft/ishell@v2.0.0+incompatible/ishell.go:99 +0x28
github.com/juruen/rmapi/shell.RunShell({0x1692840, 0xc000610020}, 0xc0001ac900, {0xc000188020, 0x0, 0x0})
	/home/runner/work/rmapi/rmapi/shell/shell.go:80 +0xdc5
main.main()
	/home/runner/work/rmapi/rmapi/main.go:80 +0x334

Upon inspection, the Pagedata file in the archive returned by get consists exclusively of the single word Blank