fix: prevent division by zero in intHandler when no events received

Summary

Fix a potential division by zero crash in the intHandler signal
handler when Sysmon is stopped before processing any events
(totalEvents == 0).

Problem

In intHandler(), the following line:

printf("Total events: %ld, bad events: %ld, ratio = %f\n", 
    totalEvents, badEvents, (double)badEvents / totalEvents);

...will produce a division by zero (resulting in NaN or crash) if
Sysmon is interrupted immediately after startup before any eBPF
events are received.

Fix

Guard the division with a ternary check:

(double)badEvents / totalEvents
→
totalEvents > 0 ? (double)badEvents / totalEvents : 0.0

Testing

• Start Sysmon and immediately send SIGINT (Ctrl+C)
• Confirm clean output showing ratio = 0.000000 instead of crash/NaN

Notes

• No functional change to normal operation
• Zero risk of regression
• Fixes undefined behavior per C standard (integer division by zero)