PG&E Corp. stock cratered Monday after the company said it will file for Chapter 11 bankruptcy protection amid the financial anguish stemming from its part in helping spark a wave of historic wildfires in California. Shares of the company dropped nearly 50 percent in early trading Monday, one day after the company said Chief Executive Geisha Williams was stepping down. The company provided the official 15-day advance notice that it and its wholly owned subsidiary, Pacific Gas and Electric, intend to file petitions to reorganize under Chapter 11 of the U.S. Bankruptcy Code on or about Jan. 29.