System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> GLib.GException: Fatal error in PNG image file: Write Error
   at Gdk.Pixbuf.Save(String filename, String type)
   at Pinta.Core.PixbufExtensions.SaveUtf8(Pixbuf pb, String filename, String type)
   at Pinta.Core.GdkPixbufFormat.DoSave(Pixbuf pb, String fileName, String fileType, Window parent)
   at Pinta.Core.GdkPixbufFormat.Export(Document document, String fileName, Window parent)
   at Pinta.Actions.SaveDocumentImplmentationAction.SaveFile(Document document, String file, FormatDescriptor format, Window parent)
   at Pinta.Actions.SaveDocumentImplmentationAction.SaveFileAs(Document document)
   at Pinta.Actions.SaveDocumentImplmentationAction.Activated(Object sender, DocumentCancelEventArgs e)
   at Pinta.Core.FileActions.RaiseSaveDocument(Document document, Boolean saveAs)
   at Pinta.Core.Document.Save(Boolean saveAs)
   at Pinta.Actions.SaveDocumentAsAction.Activated(Object sender, EventArgs e)
   at Pinta.Core.Command.<.ctor>b__33_0(Object o, ActivatedArgs args)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Span`1& arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at GLib.Signal.ClosureInvokedCB(Object o, ClosureInvokedArgs args)
   at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)