Mumbai, February 19 The benchmark Sensex fell by 1,236 points or 1.5 per cent, while the Nifty closed near 25,450 on Thursday, following a broad sell-off amid escalating geopolitical tensions between the US and Iran.Halting a three-day winning streak, the 30-share BSE Sensex plunged 1,236.11 points, or 1.48 per cent, to close at 82,498.14.The 50-share NSE Nifty declined by 365 points, or 1.41 per cent, to close at 25,454.35.Among the Sensex constituents, IndiGo, Mahindra & Mahindra...