By Dan Weil If you want ‘quality’ themes in this environment, ‘we recommend owning stocks with stable growth,’ Goldman says. Stocks are stumbling as economic growth slows and the Federal Reserve tightens financial conditions. The S&P 500 has dropped 13% this year. So what’s an investor to do? “For investors seeking to own ‘quality’ themes in a decelerating growth and tightening financial conditions environment, we recommend owning stocks with stable growth,” Goldman Sachs strategists wrote in a commentary. “Stable growth stocks and minimum volatility strategies typically outperform as economic…