我正在尝试生成签名的apk，但我一直遇到这个错误。我在谷歌上搜索错误，但没有找到可靠的答案。任何帮助都会很好。谢谢您。

Task :app:processReleaseManifest FAILED [com.facebook.android:audience-network-sdk:6.4.0] /Users/xxxx/.gradle/caches/transforms-2/files-2.1/1208b0b00589b6f8b9220695fa10ec7b/audience-network-sdk-6.4.0/AndroidManifest.xml:12:9-55 Error:  Missing 'package' key attribute on element package at [com.facebook.android:audience-network-sdk:6.4.0] AndroidManifest.xml:12:9-55 [com.facebook.android:audience-network-sdk:6.4.0] /Users/xxxx/.gradle/caches/transforms-2/files-2.1/1208b0b00589b6f8b9220695fa10ec7b/audience-network-sdk-6.4.0/AndroidManifest.xml Error:  Validation failed, exiting

See http://g.co/androidstudio/manifest-merger for more information about the manifest merger.

Execution failed for task ':app:processReleaseManifest'.
> Manifest merger failed with multiple errors, see logs