Fix RSS item link empty <link/>

[ccjjxl]

Fix RSS item link empty

panic: runtime error: index out of range [0] with length 0

goroutine 40 [running]:
github.com/glanceapp/glance/internal/feed.getItemsFromRSSFeedTask({{0xc000121aa0, 0x2a}, {0x0, 0x0}, 0x1, 0x1, {0x0, 0x0}})
	/home/ccjjxl/data/dev/glance/internal/feed/rss.go:103 +0xaaf
github.com/glanceapp/glance/internal/feed.workerPoolDo[...].func1()
	/home/ccjjxl/data/dev/glance/internal/feed/requests.go:193 +0x14d
created by github.com/glanceapp/glance/internal/feed.workerPoolDo[...] in goroutine 24
	/home/ccjjxl/data/dev/glance/internal/feed/requests.go:189 +0xff
exit status 2

[svilenmarkov]

Thanks for contributing!