Handle KeyError in Capacitor calculate_217f_part_stress()

[weibullguy]

Expected Behavior

Calculation method continues to calculate remaining values even if there are missing input values used to select from dicts.

Actual Behavior

Method raises KeyError when missing input value prevents selecting dict value. Selecting a new component/assembly does not 'reset' anything and RTK must be closed and re-opened.

Steps to Reproduce the Problem

1. Select a capacitor using the part stress method.
2. Don't fully populate all inputs.
3. Attempt to calculate part.

Operating Environment

• Operating System: Linux
• OS Distribution (if Linux): Slackware
• OS Version: 14.2
• Hardware: ASUS laptop wit Core i7
• Required Software Versions:
  • Python == 2.7.5
  • defusedxml == 0.5.0
  • lifelines == 0.13.0
  • lxml == 4.1.1
  • matplotlib == 1.4.3
  • numpy == 1.13.3
  • pandas == 0.21.1
  • pypubsub == 3.3.0
  • scipy == 1.0.0
  • sortedcontainers == 1.5.9
  • sqlalchemy == 1.2.0
  • sqlalchemy_utils == 0.32.21
  • statsmodels == 0.8.0
  • treelib == 1.5.1
  • xlrd==1.1.0
  • xlwt==1.3.0

[weibullguy]

This was fixed in a previous commit, but which one is unknown.