Grid with Frame->All: How to not draw frames around empty cells?

You may use Item.

Grid@Map[Item[#, Frame -> All] &, Partition[Range@17, UpTo@7], {2}]

Hope this helps.

Adapted from the "Frame specific elements" example in the docs for Grid under the subsection Options > Frame:

With[{items = Partition[Range@17, UpTo@7]},
 Grid[items, Frame -> {None, None, Thread[Position[items, _, {2}] -> True]}]
 ]