RGBA fails to parse if alpha is missing

[ebshimizu]

According to the CSS spec the alpha parameter in the rgba color string is optional:

<modern-rgba-syntax> = rgba( [ <number> | <percentage> | none ]{3} [ / [ <alpha-value> | none ] ]? )

Tinycolor fails to parse cases where rgba() colors string have no alpha because it expects exactly four values when it should be expecting three and an optional fourth:

TinyColor/tinycolor.js

Line 1039 in b49018c

rgba: new RegExp("rgba" + PERMISSIVE_MATCH4),