Unity 2019.3 just officially available and spine runtime show the following error:
NullReferenceException: Object reference not set to an instance of an object
Spine.Unity.SkeletonDataCompatibility.GetCompatibilityProblemInfo (Spine.Unity.SkeletonDataCompatibility+VersionInfo fileVersion) (at Assets/AddOns/Spine/Runtime/spine-unity/Asset Types/SkeletonDataCompatibility.cs:134)
Spine.Unity.Editor.AssetUtility.IsSpineData (UnityEngine.TextAsset asset, Spine.Unity.SkeletonDataCompatibility+CompatibilityProblemInfo& compatibilityProblemInfo) (at Assets/AddOns/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs:668)
Spine.Unity.Editor.AssetUtility.ImportSpineContent (System.String[] imported, System.Boolean reimport) (at Assets/AddOns/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs:270)
Spine.Unity.Editor.AssetUtility.HandleOnPostprocessAllAssets (System.String[] imported) (at Assets/AddOns/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs:90)
Spine.Unity.Editor.SpineEditorUtilities.OnPostprocessAllAssets (System.String[] imported, System.String[] deleted, System.String[] moved, System.String[] movedFromAssetPaths) (at Assets/AddOns/Spine/Editor/spine-unity/Editor/Utility/SpineEditorUtilities.cs:74)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <437ba245d8404784b9fbab9b439ac908>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <437ba245d8404784b9fbab9b439ac908>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <437ba245d8404784b9fbab9b439ac908>:0)
UnityEditor.AssetPostprocessingInternal.InvokeMethod (System.Reflection.MethodInfo method, System.Object[] args) (at <3b74787e58694cdda2c241162159b3b7>:0)
UnityEditor.AssetPostprocessingInternal.PostprocessAllAssets (System.String[] importedAssets, System.String[] addedAssets, System.String[] deletedAssets, System.String[] movedAssets, System.String[] movedFromPathAssets) (at <3b74787e58694cdda2c241162159b3b7>:0)