KEY TAKEAWAYSWells Fargo shares sank Friday after the lender reported a slump in second-quarter net interest income that offset higher-than-forecast results.Net interest income, a key measure of lending profitability, fell about 9% year-over-year to $11.9 billion during the three months ended June 30. The slump in net interest income overshadowed results that beat Wall Street analysts' estimates. Wells Fargo (WFC) shares sank Friday after the lender reported a slump in second-quarter net interest income tha ...