A top Nvidia executive said President Trump’s potential tariffs and export controls on its powerful computer chips remain an “unknown” — sending its stock sliding despite better-than-expected quarterly profits.Nvidia shares were off more than 4% Thursday morning as investor digested a mixed outlook from CEO Jensen Huang’s firm in its fourth quarter earnings report. Wall Street remains anxious about macroeconomic factors as Trump ramps up the pressure on China. Nvidia CFO Colleen Kress acknowledged the uncer ...