Imputing Missing values into a heatmap

Basically, I 'm making a heatmap that has connection patterns between a phone and device I am working with. the Y would have columns like (Action, processing_command, locked, connected, connecting, etc). The X-axis is the time at which a particular event is logged. The values are True/False/nan, in the sense that if a phone is processing a command it would have True in processing_command, False in locked, nan in action, for example.

I have a preliminary heatmap working, and even added a rangeslider on x to be able to more accurately look at specific times of actions and the connection pattern. The main issue I am running into is how to get the missing date values (when there are no logs and therefore no data to plot) to show up as nan/blank instead of staying the same value as the last log.
Essentially, when i look at my heatmap, it shows the data as if it is continuous, when there should be gaps in the data to show when there arent any logs recorded.

My idea was to somehow impute the missing date values and then add corresponding nan for all columns to those dates but Iā€™m not sure how feasible that is in the long run.
Let me know if I need to explain the issue any further, thanks!

EDIT: figured out how to add an image. To give you an example of my issue, Theres a log recorded on April 25, and the next log recorded is on May 2nd. How do i make it so the gap between those dates is nan/empty instead of showing that its continuous as it shows here.