Is my bulb safe to run? Bubble in glass

Hi - long time listener, first time caller - I just got a 400w HPS and it has a small bubble in the glass near the base, do ya'll think it's safe to run? It's very small and I took the picture with my phone so sorry about the quality.

Bumpelstiltskin.

On a related question how many of you guys have blown bulbs? Was it time, fingerprints, or some unknown thing?