filtering null values from the identify properties

- resetting values to null may cause inconsistent cross device tracking

vector/src/main/java/im/vector/app/features/analytics/impl/DefaultVectorAnalytics.kt

@@ -176,7 +176,7 @@ class DefaultVectorAnalytics @Inject constructor(
     }
 
     override fun updateUserProperties(identity: Identity) {
-        posthog?.identify(REUSE_EXISTING_ID, identity.getProperties().toPostHogProperties(), IGNORED_OPTIONS)
+        posthog?.identify(REUSE_EXISTING_ID, identity.getProperties()?.toPostHogUserProperties(), IGNORED_OPTIONS)
     }
 
     private fun Map<String, Any?>?.toPostHogProperties(): Properties? {
@@ -186,4 +186,14 @@ class DefaultVectorAnalytics @Inject constructor(
             putAll(this@toPostHogProperties)
         }
     }
+
+    /**
+     * We avoid sending nulls as part of the UserProperties as this will reset the values across all devices
+     * The Identify event has nullable properties to allow for clients to opt in
+     */
+    private fun Map<String, Any?>.toPostHogUserProperties(): Properties {
+        return Properties().apply {
+            putAll(this@toPostHogUserProperties.filter { it.value != null })
+        }
+    }
 }