Crash when datalogging MPU-6050 to SD card

This seems to be fixed. I've connected the modules together using short soldered leads rather than the breadboard and it's just run for 18 and a half hours before I decided to stop the test. Previously the maximum run time was less than an hour. So even with SPI at sixteenth speed and I2C at 50kHz instead of 400kHz, it seems a breadboard is too flaky when both comms mechanisms are in use. I note I didn't actually say I was on breadboard- in hindsight maybe that would've prompted immediate comment but I thought at slow data rates I'd be ruling out such things.