Fix regression clicking same spot w/Rectangular Marquee to deselect

Regression introduced in 26c1a94b833c2e0b56ea6300f8b14e14ada58c62

Reported:
- https://community.aseprite.org/t/12491/1
- https://steamcommunity.com/app/431730/discussions/0/3200371016617015005/

src/app/ui/editor/drawing_state.cpp

@@ -242,12 +242,18 @@ bool DrawingState::onMouseMove(Editor* editor, MouseMessage* msg)
   // Update velocity sensor.
   m_velocity.updateWithScreenPoint(msg->position());
 
+  // Update pointer with new mouse position
   m_lastPointer = tools::Pointer(gfx::Point(m_delayedMouseMove.spritePos()),
                                  m_velocity.velocity(),
                                  button_from_msg(msg),
                                  msg->pointerType(),
                                  msg->pressure());
 
+  // Indicate that we've received a real mouse movement event here
+  // (used in the Rectangular Marquee to deselect when we just do a
+  // simple click without moving the mouse).
+  m_mouseMoveReceived = true;
+
   // Use DelayedMouseMove for tools like line, rectangle, etc. (that
   // use the only the last mouse position) to filter out rapid mouse
   // movement.
@@ -347,8 +353,6 @@ void DrawingState::onExposeSpritePixels(const gfx::Region& rgn)
 
 void DrawingState::handleMouseMovement()
 {
-  m_mouseMoveReceived = true;
-
   // Notify mouse movement to the tool
   ASSERT(m_toolLoopManager);
   m_toolLoopManager->movement(m_lastPointer);