Fix #423 (node blunder colors in the default theme)

[kaorahi]

I'm afraid most users may not notice the feature #413 because of the issue #423. This PR applies the proposed parameters in #423 (comment) if they are empty. It works only once so that users can still set them empty again if they like.

related: #800 #801

[hope366]

I have been using lizzie with this PR for quite some time.
Right now, when I put that lizzie in the official lizzie 0.7.4 folder and started it, the winning percentage change node was left blank.
In the official lizzi 0.7.4, the winning percentage change node is blank by default, so I thought this PR would work. Is this recognition wrong?

[kaorahi]

thx. It seems broken for some reason. Please apply 64dc629 to fix it.

When you test it, you need to delete (or rename) both files config.txt and persist.

[hope366]

I tried the modified version and it seems to work fine. Thank you very much.
When I started lizzie after deleting "config.txt", an error occurred because the part of the engine command that should be "./leelazero/leelaz.exe" is "./leelaz". It worked normally by rewriting it correctly.

[kaorahi]

I found the above "some reason". The name of the default theme is inconsistent between Config.java ("default") and ConfigDialog.java ("Default" in English, or i18n names in other languages).

So 64dc629 can fail in non-English environments. The correct fix should be cd14ee8. Namely, we do not need to check the default theme here because we never touch theme/yasnaya/theme.txt anyway in checkEmptyBlunderThresholds from validateAndCorrectSettings.

cd14ee8 should work when all the following conditions are satisfied.

1. "blunder-winrate-thresholds" and "blunder-node-colors" are both empty in config.txt.
2. "checked-empty-blunder-thresholds" is not true in persist.