[Chore]: Fix Android bindings (#4095)

* [Chore]: Add GenericPhantomReference.java

* [Chore]: Fix unnecessary null assertion in WalletCoreLibLoader.kt

codegen/lib/templates/java/class.erb

@@ -1,5 +1,5 @@
 import java.security.InvalidParameterException;
-import java.util.HashSet;
+import wallet.core.java.GenericPhantomReference;
 
 <%  less = entity.static_methods.detect{ |i| i.name == 'Less' } -%>
 <%  equal = entity.static_methods.detect{ |i| i.name == 'Equal' } -%>
@@ -21,7 +21,7 @@ public final class <%= entity.name %> {
         <%= entity.name %> instance = new <%= entity.name %>();
         instance.nativeHandle = nativeHandle;
 <%  unless entity.methods.select{ |x| x.name == "Delete" }.empty? -%>
-        <%= entity.name %>PhantomReference.register(instance, nativeHandle);
+        GenericPhantomReference.register(instance, nativeHandle, <%= entity.name %>::nativeDelete);
 <%  end -%>
         return instance;
     }
@@ -96,9 +96,7 @@ public final class <%= entity.name %> {
             throw new InvalidParameterException();
         }
 
-        GenericPhantomReference.register(someObject, someHandle, handle -> {
-            nativeDelete(nativeHandle);
-        });
+        GenericPhantomReference.register(this, nativeHandle, <%= entity.name %>::nativeDelete);
     }
 
 <%- end -%>

jni/java/wallet/core/java/GenericPhantomReference.java

@@ -0,0 +1,51 @@
+package wallet.core.java;
+
+import java.lang.ref.PhantomReference;
+import java.lang.ref.ReferenceQueue;
+import java.util.Set;
+import java.util.HashSet;
+
+public class GenericPhantomReference extends PhantomReference<Object> {
+    private final long nativeHandle;
+    private final OnDeleteCallback onDeleteCallback;
+
+    private static final Set<GenericPhantomReference> references = new HashSet<>();
+    private static final ReferenceQueue<Object> queue = new ReferenceQueue<>();
+
+    static {
+        Thread finalizingDaemon = new Thread(() -> {
+            try {
+                doDeletes();
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        });
+        finalizingDaemon.setName("WCFinalizingDaemon");
+        finalizingDaemon.setDaemon(true);
+        finalizingDaemon.setPriority(Thread.NORM_PRIORITY);
+        finalizingDaemon.start();
+    }
+
+    private GenericPhantomReference(Object referent, long handle, OnDeleteCallback onDelete) {
+        super(referent, queue);
+        this.nativeHandle = handle;
+        this.onDeleteCallback = onDelete;
+    }
+
+    public static void register(Object referent, long handle, OnDeleteCallback onDelete) {
+        references.add(new GenericPhantomReference(referent, handle, onDelete));
+    }
+
+    private static void doDeletes() throws InterruptedException {
+        GenericPhantomReference ref = (GenericPhantomReference) queue.remove();
+        for (; ref != null; ref = (GenericPhantomReference) queue.remove()) {
+            ref.onDeleteCallback.nativeDelete(ref.nativeHandle);
+            references.remove(ref);
+        }
+    }
+
+    @FunctionalInterface
+    public interface OnDeleteCallback {
+        void nativeDelete(long handle);
+    }
+}

kotlin/wallet-core-kotlin/src/commonAndroidJvmMain/kotlin/com/trustwallet/core/WalletCoreLibLoader.kt

@@ -34,9 +34,9 @@ object WalletCoreLibLoader {
     }
 
     private fun getLibResourcePath(): String {
-        val osNameOriginal = System.getProperty("os.name").lowercase()
+        val osNameOriginal = System.getProperty("os.name")!!.lowercase()
         val osName = osNameOriginal.lowercase()
-        val archOriginal = System.getProperty("os.arch").lowercase()
+        val archOriginal = System.getProperty("os.arch")!!.lowercase()
         val arch = archOriginal.lowercase()
 
         return when {