sort out before/frank.csv has a missing value (!)

[maxheld83]

migrated from maxheld83/keyneson#4

before/Frank.csv has an empty cell; the pictures and scans reveal at this cell an invalid card, namely the "very much disagree" card that participants should have placed to the bottom left and right of the distribution.

In addition, the agree very much card is placed on top of the entire distribution, which also makes no sense.

This raises some doubts as to whether the participant understood the procedure, and what should be done with the missing value.

Maybe get back to the participant.