Fix onEffects not called when subscriptions are removed

[jonaskello]

The onEffects() function is not called if Program.subscription() returns undefined. This causes problems becuse the previous call may have returned a subscription and that caused a call to onEffects() which then did setup some subscription. Then the program is no longer interested in the subscription so it returns undefined from Program.subscription(). Now the effect manager should terminate the underlying subscription but since onEffects() is not called it does not.

The problematic code is here. It is an attempt at optimizing the calls to onEffects() and only call the effect managers that actually has gathered effects. This works well for Cmd becuase in that case undefined means there is no command to execute. However for subscriptions undefined means the program wants no subscriptions which is significant if the program previously wanted subscriptions.

This line only calls effect managers that has gathered effects. This PR will change to all effect managers are always called and the ones that does not have any Cmd or Sub will recieve undefined on those parameters.

[codecov]

Codecov Report

Merging #8 (4099835) into master (2e7a0e9) will increase coverage by 5.22%.
The diff coverage is 63.33%.

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
+ Coverage   63.44%   68.67%   +5.22%     
==========================================
  Files           8       11       +3     
  Lines         145      166      +21     
  Branches       26       28       +2     
==========================================
+ Hits           92      114      +22     
+ Misses         52       51       -1     
  Partials        1        1              

Impacted Files	Coverage Δ
src/__tests__/helpers/mock-effect-manager.ts	50.00% <50.00%> (ø)
src/program.ts	79.68% <50.00%> (+5.91%)	⬆️
src/__tests__/helpers/mock-program.ts	87.50% <87.50%> (ø)
src/__tests__/helpers/mock-render.ts	100.00% <100.00%> (ø)
src/effect-manager.ts	88.88% <0.00%> (+33.33%)	⬆️

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