fix: properly filter palettes

[CGNonofr]

• I have followed (at least) the PR section of the contributing guide.

If there is a palette with a main non-string field, it crashes

[DiegoAndai]

Hi @CGNonofr, thanks for the report.

What value are you providing to the main field? It should be a string, it's types as such: https://github.com/mui/material-ui/blob/next/packages/mui-material/src/styles/createPalette.d.ts#L44

[CGNonofr]

Hi @CGNonofr, thanks for the report.

What value are you providing to the main field? It should be a string, it's types as such: https://github.com/mui/material-ui/blob/next/packages/mui-material/src/styles/createPalette.d.ts#L44

PaletteColorOptions is only used for the primary, secondary, error, warning, info and success.

The problem is it is looping of every palettes keys, not only those corresponding to a PaletteColorOptions.

This is not a problem for other predefined fields because none has a main property, but we added a custom palette field with a main field of type object.