Exception when trying to save a new image twice

[Maia Everett]

To reproduce:
- Create a new image.
- Save it under any filename.
- Press the save button again.

This results in an error box (I tried to save to /tmp/x.png).

Unhandled exception:
Exception has been thrown by the target of an invocation.

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> GLib.GException: Failed to open 'Untitled1/x.png' for writing: No such file or directory
  at Gdk.Pixbuf.Save (System.String filename, System.String type) [0x00000]
  at Pinta.Core.FileActions.SaveFile (System.String file, System.String filetype) [0x00000]
  at Pinta.Core.FileActions.HandlePintaCoreActionsFileSaveActivated (System.Object sender, System.EventArgs e) [0x00000]
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000]
  --- 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]
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000]
  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000]
  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000]
  at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000]
  at GLib.Signal.ClosureInvokedCB (System.Object o, GLib.ClosureInvokedArgs args) [0x00000]
  at GLib.SignalClosure.Invoke (GLib.ClosureInvokedArgs args) [0x00000]
  at GLib.SignalClosure.MarshalCallback (IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data) [0x00000]

Choosing "Save as" and then saving to the same file does not have this problem.

[Maia Everett (linneris)]

In master now.

[Jonathan Pobst (jpobst)]

http://github.com/jpobst/Pinta/commit/f1d7aa2b34011929e3c45b980b1733346a20ba9f