[dumpling] Now actually add differential count.

Before we were printing 0 always.

Bug: 441467877
Change-Id: Icacd9310f8cd845695d2a83e5eb297ce2e60882b
Reviewed-on: https://chrome-internal-review.googlesource.com/c/v8/fuzzilli/+/8977177
Reviewed-by: Matthias Liedtke <mliedtke@google.com>
Commit-Queue: Danylo Mocherniuk <mdanylo@google.com>

Author: Danylo Mocherniuk

Sources/Fuzzilli/Modules/Statistics.swift

@@ -136,6 +136,9 @@ public class Statistics: Module {
         fuzzer.registerEventListener(for: fuzzer.events.CrashFound) { _ in
             self.ownData.crashingSamples += 1
         }
+        fuzzer.registerEventListener(for: fuzzer.events.DifferentialFound) { _ in
+            self.ownData.differentialSamples += 1
+        }
         fuzzer.registerEventListener(for: fuzzer.events.TimeOutFound) { _ in
             self.ownData.timedOutSamples += 1
             self.correctnessRate.add(0.0)