handle error conditions when checking memory usage of jedi language server process

[DonJayamanne]

Fixes #926

[codecov]

Codecov Report

Merging #927 into master will decrease coverage by <.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #927      +/-   ##
==========================================
- Coverage   64.07%   64.07%   -0.01%     
==========================================
  Files         260      260              
  Lines       12042    12044       +2     
  Branches     2133     2134       +1     
==========================================
+ Hits         7716     7717       +1     
- Misses       4317     4318       +1     
  Partials        9        9

Impacted Files	Coverage Δ
src/client/providers/jediProxy.ts	72.01% <66.66%> (-0.11%)	⬇️

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