Graph data in Variables Panel disappear when there are over 6 saved runs

[emilykuang]

Steps to reproduce

• Open simulation
• Change parameters and save run 6 times
• On the 7th time, there is an undefined error in MultiLinePlot.vue and the lines in the Variables Panel stop showing up

Update: This issue occurs for different models too. For example, when you run the first model 3 times, then switch to another model and run 3 times, on the 4th run, the error will show up and the graphs disappear. (Need to refresh the webpage to reset saved data and runs counter)

In the screen recording, note the number of runs in the settings bar of the variables panel (every time it gets to 7, the error is thrown)
https://user-images.githubusercontent.com/23723378/130118927-5dd94751-d755-49f2-a9c7-85b04f7d1bb9.mov

[mj3cheun]

Resolve before hiatus