Fix for ANSI color codes that include blank values

[jaysonlarose]

Hey, y'all.

I got the developer of wezterm to add a "Copy as ANSI" option, but the truecolor ANSI codes it outputs have some blank values in them (they look like <esc>[48:2::255:180:69m). This here's a fix so that they get parsed correctly.

[ssbarnea]

@jaysonlarose Please investigate why tests are failing, we cannot merge it with them not passing.

[jaysonlarose]

Oh, I see.

            try:
                params = [int(x) for x in re.split("[;:]", params) if len(x) > 0]
            except ValueError:
                params = [ANSI_FULL_RESET]

The converter is relying on that exception handler being used to interpret \x1b[m as an ANSI_FULL_RESET.

[jaysonlarose]

I've switched to a slightly hackier way of removing blank fields. This one passes tests.