Fix clearing behaviour

Author: maciejburda

dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/internal/DatadogCore.kt

@@ -270,7 +270,7 @@ internal class DatadogCore(
     }
 
     override fun setAnonymousId(anonymousId: UUID?) {
-        coreFeature.userInfoProvider.setAnonymousId(anonymousId.toString())
+        coreFeature.userInfoProvider.setAnonymousId(anonymousId?.toString())
     }
 
     override fun isCoreActive(): Boolean = isActive

dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/DatadogCoreTest.kt

@@ -245,6 +245,19 @@ internal class DatadogCoreTest {
         verify(mockUserInfoProvider).setAnonymousId(uuid.toString())
     }
 
+    @Test
+    fun `M clears anonymousId W setAnonymousId(null)`() {
+        // Given
+        val mockUserInfoProvider = mock<MutableUserInfoProvider>()
+        testedCore.coreFeature.userInfoProvider = mockUserInfoProvider
+
+        // When
+        testedCore.setAnonymousId(null)
+
+        // Then
+        verify(mockUserInfoProvider).setAnonymousId(null)
+    }
+
     @Test
     fun `M set additional user info W addUserProperties() is called`(
         @StringForgery(type = StringForgeryType.HEXADECIMAL) id: String,