Occasional Unhandled Exception when Changing Dot Type in Continuity Editor

[kmdurand]

How to recreate:

• Make a sheet with multiple dot types (at least 3 types)
• Write continuities for each dot type
• Reset all dots to plain type
• Open continuity editor
• Select the second to last available dot type in the menu
• Clear the continuity for that dot type
• Select the last available dot type in the menu
• You will be prompted about whether or not you want to save - specify that you would like to save
  You should get an unhandled exception.

[rmpowell77]

Fixed in #97