insights: panic when queue worker initailizes with an empty queue

Created by: coury-clark

When the insights query queue worker initializes with an empty queue it tries to return an out of bounds index in the job list. This would cause the query worker to fail to initialize until the worker node it is running on is restarted.

INFO Updating insights/historical-worker rate limit value=10 [enterprise-worker] 2021/08/31 19:44:47 goroutine panic: runtime error: index out of range [0] with length 0 [enterprise-worker] goroutine 594 [running]: [enterprise-worker] runtime/debug.Stack(0xc001f87648, 0x2c81880, 0xc0007e6db0)