Add-in crashes installing from unknown file type

[grofaty]

Pinta 1.6 from pinta-daily PPA on Ubuntu 14.04.

1. Add-ins | Add-in Manager.
2. On bottom click on "Install from file" button.
3. From files select "All files".
4. Point to some text file like test.txt and clik Open button.
Pinta crashes with error:
============
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> ICSharpCode.SharpZipLib.Zip.ZipException: Cannot find central directory
  at ICSharpCode.SharpZipLib.Zip.ZipFile.ReadEntries () [0x00000] in <filename unknown>:0
  at ICSharpCode.SharpZipLib.Zip.ZipFile..ctor (System.String name) [0x00000] in <filename unknown>:0
  --- End of inner exception stack trace ---
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0
  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0
  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0
  at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in <filename unknown>:0
  at GLib.Signal.ClosureInvokedCB (System.Object o, GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.Invoke (GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.MarshalCallback (IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data) [0x00000] in <filename unknown>:0
============

Crash should not happen. It should just report message that this is not valid package file type.

[Cameron White (cameronwhite91)]

This dialog comes from the Mono add-in library, and will need to be fixed upstream (https://github.com/mono/mono-addins)