Jamstats misses data when jammer/pivot data are inconsistently available

[dhmay]

Describe the bug
If skater data (jammer/pivot and/or lineup tracking) are available for every jam, Jamstats works fine.

If skater data are unavailable for every jam, Jamstats leaves out the skater plots and otherwise works fine.

If skater data are available for some jams but not for others, Jamstats will leave out the data from all jams without the skater data. Instead, it should include the skater data where available but still retain the jam data for all jams.