No longer working for forecast length > time interval

[tsmbland]

If the forecast length is set to greater than the time interval, the model doesn't work any more (no investments).

Previously, this bit of code would get demands for the forecast year:

# > to sector timeslice
        market = self.convert_market_timeslice(
            mca_market.sel(
                commodity=self.technologies.commodity, region=self.technologies.region
            ).interp(
                year=sorted(
                    {
                        current_year,
                        current_year + time_period,
                        current_year + self.forecast,
                    }
                ),
                **self.interpolation,
            ),
            self.timeslices,
        )

I got rid of this in v1.3.0, so now demands for the forecast year are unspecified/blank unless the forecast length equals the time period. This gets interpreted as zero demands, so no investments are made. Oops (although we're changing how forecast is done anyway so maybe it's fine)

[tsmbland]

No longer a bug as I'm working towards fully removing the forecast feature