Bug with "Max Time" input

[daattali]

To reproduce:

• Have only one drug in the table
• Set the time to 20
• Set "Max Time" to 10 (it was previously 60 by default)
• You'll get a nothing plot. Now set Max Time back to 60 -- nothing happens. You must set Max Time to some other value and then back to 60 in order for the plot to come back