fix(controller): Handling panic in leader election

[sarabala1979]

Signed-off-by: Saravanan Balasubramanian sarabala1979@gmail.com

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  closes leader election panic: nil pointer deref #6071

[codecov]

Codecov Report

Merging #6072 (a75144f) into master (803855b) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #6072   +/-   ##
=======================================
  Coverage   47.54%   47.55%           
=======================================
  Files         248      248           
  Lines       15733    15734    +1     
=======================================
+ Hits         7480     7482    +2     
  Misses       7318     7318           
+ Partials      935      934    -1     

Impacted Files	Coverage Δ
workflow/controller/controller.go	20.61% <0.00%> (-0.04%)	⬇️
cmd/argoexec/commands/emissary.go	50.00% <0.00%> (+1.56%)	⬆️

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