Correct the encoding of the glyph-substitution table in several families

**Describe the bug**
According to the specification, neither version 1.0 nor 1.1 of `GSUB` can have `scriptListOffset`, `featureListOffset`, and `lookupListOffset` set to zero (NULL):

https://learn.microsoft.com/en-us/typography/opentype/spec/gsub#gsub-header

In this and several other families, however, they are zero.

**To Reproduce**
```shell
ttx -t GSUB ofl/londrinasolid/LondrinaSolid-Thin.ttf
```

More generally, all these are affected:

```
ofl/londrinasolid/LondrinaSolid-Light.ttf
ofl/londrinasolid/LondrinaSolid-Regular.ttf
ofl/londrinasolid/LondrinaSolid-Thin.ttf
ofl/londrinasolid/LondrinaSolid-Black.ttf
ofl/londrinasketch/LondrinaSketch-Regular.ttf
ofl/mashanzheng/MaShanZheng-Regular.ttf
ofl/federant/Federant-Regular.ttf
ofl/longcang/LongCang-Regular.ttf
ofl/londrinashadow/LondrinaShadow-Regular.ttf
ofl/zhimangxing/ZhiMangXing-Regular.ttf
ofl/liujianmaocao/LiuJianMaoCao-Regular.ttf
```

**Expected behavior**
They should not be zero.

I would appreciate if someone could confirm; I might be misunderstanding the specification. Thank you!