Crash after pasting image into new image and click out of canvas

[grofaty]

Tested on 1.7+r1124-202008021721~ubuntu18.04.1:

1. Assuming image is opened. Select whole image with CTRL+A
2. Copy image: CTRL+C
3. Paste into new image: CTRL+ALT+V
4. Click outside of canvas and crash appears:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object
  at Pinta.Tools.MoveSelectedTool.OnFinishTransform (Cairo.Matrix transform) [0x0005b] in <8ce32c76724a4e74b1d4b25621da1929>:0
  at Pinta.Tools.BaseTransformTool.OnMouseUp (Gtk.DrawingArea canvas, Gtk.ButtonReleaseEventArgs args, Cairo.PointD point) [0x0000f] in <8ce32c76724a4e74b1d4b25621da1929>:0
  at Pinta.Core.BaseTool.DoMouseUp (Gtk.DrawingArea canvas, Gtk.ButtonReleaseEventArgs args, Cairo.PointD point) [0x00030] in <e7d0dcd7669a474795360fb5061850db>:0
  at Pinta.Gui.Widgets.PintaCanvas+<PintaCanvas>c__AnonStorey0.<>m__3 (System.Object sender, Gtk.ButtonReleaseEventArgs e) [0x00038] in <f5200e1e2aa9441e9decd3de04b781a0>:0
  at (wrapper managed-to-native) System.Reflection.RuntimeMethodInfo.InternalInvoke(System.Reflection.RuntimeMethodInfo,object,object[],System.Exception&)
  at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x0006a] in <a17fa1457c5d44f2885ac746c1764ea5>:0
   --- End of inner exception stack trace ---
  at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00083] in <a17fa1457c5d44f2885ac746c1764ea5>:0
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <a17fa1457c5d44f2885ac746c1764ea5>:0
  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x000e7] in <a17fa1457c5d44f2885ac746c1764ea5>:0
  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00008] in <a17fa1457c5d44f2885ac746c1764ea5>:0
  at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in <a17fa1457c5d44f2885ac746c1764ea5>:0
  at GLib.Signal.ClosureInvokedCB (System.Object o, GLib.ClosureInvokedArgs args) [0x0007d] in <ed39f21b9e9343dcbd442a17ad356a9f>:0
  at GLib.Signal+SignalClosure.Invoke (GLib.ClosureInvokedArgs args) [0x0000c] in <ed39f21b9e9343dcbd442a17ad356a9f>:0
  at GLib.Signal+SignalClosure.MarshalCallback (System.IntPtr raw_closure, GLib.Value* return_val, System.UInt32 n_param_vals, GLib.Value* param_values, System.IntPtr invocation_hint, System.IntPtr marshal_data) [0x000b1] in <ed39f21b9e9343dcbd442a17ad356a9f>:0

[grofaty (grofaty)]

Additional test:

5. If new tab is closed and saving dismissed and now click outside of first canvas and crash appears also for first tab.

[grofaty (grofaty)]

It looks like even much simpler way to reproduce a problem:
1. Click on Move Selected Pixels icon.
2. Click outside of canvas and crash appears.

And crash also appears in step 2, if in step one Move Selection is chosen.

[Cameron White (cameronwhite91)]

Fixed by https://github.com/PintaProject/Pinta/commit/fbc04f5c9a1b4b1d9a51c0bbc9f8f4dfd4045037

[grofaty (grofaty)]

Tested in 1.7+r1134-202008032046~ubuntu18.04.1 and I can confirm problem is fixed.