Panic when `node.nodeMessageChan <- lib.NodeErase` message is sent for the first time

When the message is sent for the first time using [node.nodeMessageChan <- lib.NodeErase](https://github.com/deso-protocol/core/blob/main/cmd/node.go#L233), it panics. This is because `node.IsRunning` is false when the message was sent. The value is set  at a [later point](https://github.com/deso-protocol/core/blob/main/cmd/node.go#L254).