Ignore empty content warnings in API (resolves #977)

What does this MR do?

Modify the Misskey and Mastodon post APIs to treat a blank / empty content warning as if it were null. This avoids a spurious validation error when posting with certain clients.

Specific changes:

• ignore empty CW with creating / editing notes
• don't parse empty strings in timelineArgs.ts
• don't use empty CW as placeholder in megalodon

Contribution Guidelines

By submitting this merge request, you agree to follow our Contribution Guidelines

• I agree to follow this project's Contribution Guidelines
• I have made sure to test this merge request

added bugbackend label

added 1 commit

• 908271c9 - ignore empty CW with creating / editing notes

Compare with previous version

marked the checklist item I have made sure to test this merge request as completed

approved this merge request

mentioned in issue #977 (closed)

added 2 commits

• 0cd12923 - disable '@typescript-eslint/prefer-nullish-coalescing' for primitive types
• 1483f96c - collapse empty `cw` to null

Compare with previous version

reset approvals from @dakkar by pushing to the branch

approved this merge request

approved this merge request

mentioned in commit a90a8e9e

merged