rule_engine.c: Fix several bugs.
rule_engine.c: Fix several bugs.

Previously crashed if:
- Version missing from request line.
- No headers.

b1v1r/ironbee,ironbee/ironbee,b1v1r/ironbee,b1v1r/ironbee,ironbee/ironbee,ironbee/ironbee,ironbee/ironbee,b1v1r/ironbee,b1v1r/ironbee,b1v1r/ironbee,ironbee/ironbee,b1v1r/ironbee,b1v1r/ironbee,ironbee/ironbee,b1v1r/ironbee,ironbee/ironbee,ironbee/ironbee,b1v1r/ironbee,ironbee/ironbee,b1v1r/ironbee,ironbee/ironbee,ironbee/ironbee,ironbee/ironbee,b1v1r/ironbee