I've encountered this before. I don't believe there is an "automatic"
solution.

Two options I'm aware of. First, define a new line chart for each data
series containing consecutive non-null data. Those separate lines will appear
as one sequence (except for the null gaps) if you'll then configure them with
the same colors, markers, etc.

The second option is to manually hide the null line segments & points (e.g.,
by coloring them white).