Comment 0 for bug 704265

I can reproduce it this way:

1. Open any image which has uppercase extension. (test.JPG)
2. Save as... (give it any name with any extension)
3. Save

And it gives me the exception:

 System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentNullException: Argument cannot be null.
Parameter name: key
  at System.Collections.Generic.Dictionary`2[Gtk.FileFilter,Pinta.Core.FormatDescriptor].get_Item (Gtk.FileFilter key) [0x00000] in <filename unknown>:0
  at Pinta.DialogHandlers.SaveFileAs (Pinta.Core.Document document) [0x00000] in <filename unknown>:0
  at Pinta.DialogHandlers.HandlePintaCoreActionsFileSaveAsActivated (System.Object sender, System.EventArgs e) [0x00000] in <filename unknown>:0
  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] 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

There is a workaround. You need to select the type of image/extension(any type) in the box in the down-right corner.