UnityNativeShare

• Unexported Activities are hidden from NativeShareCustomShareDialog to fix java.lang.SecurityException
• Attempted to fix a weird NullReferenceException in NativeShareCustomShareDialog
• Updated Unity version to 2021.3.45f2 (simplified codebase accordingly)

Fixed rare "No such proxy method" error for native callback functions

• Potential fix for IllegalStateException on Android
• Photo Library Usage Description doesn't override Xcode setting if it's empty

Fixed a native IllegalStateException

• Potential bugfix for ShareResultCallback.shareTarget being null for some apps on newest Android versions
• Potential bugfix for crash in Unity as a Library apps (#155)
• Fixed share dialog not disappearing automatically when canceling a share operation on iPhones (which could lead to share callback being called multiple times)
• Added NativeShare.Clear function