Fix crash when right clicking AUI toolbar while left button is pressed.

Ignore the unrelated mouse events during the item dragging.

This avoids a crash due to m_actionItem being NULL when right clicking an item
while the left mouse button is kept pressed.

Closes #16327.

(this is a forward port of 648d9ce1fb from 3.0)

src/aui/auibar.cpp

@@ -2673,6 +2673,9 @@ void wxAuiToolBar::OnLeftUp(wxMouseEvent& evt)
 
 void wxAuiToolBar::OnRightDown(wxMouseEvent& evt)
 {
+    if (HasCapture())
+        return;
+
     wxRect cli_rect(wxPoint(0,0), GetClientSize());
 
     if (m_gripperSizerItem)
@@ -2709,6 +2712,9 @@ void wxAuiToolBar::OnRightDown(wxMouseEvent& evt)
 
 void wxAuiToolBar::OnRightUp(wxMouseEvent& evt)
 {
+    if (HasCapture())
+        return;
+
     wxAuiToolBarItem* hitItem;
     hitItem = FindToolByPosition(evt.GetX(), evt.GetY());
 
@@ -2739,6 +2745,9 @@ void wxAuiToolBar::OnRightUp(wxMouseEvent& evt)
 
 void wxAuiToolBar::OnMiddleDown(wxMouseEvent& evt)
 {
+    if (HasCapture())
+        return;
+
     wxRect cli_rect(wxPoint(0,0), GetClientSize());
 
     if (m_gripperSizerItem)
@@ -2778,6 +2787,9 @@ void wxAuiToolBar::OnMiddleDown(wxMouseEvent& evt)
 
 void wxAuiToolBar::OnMiddleUp(wxMouseEvent& evt)
 {
+    if (HasCapture())
+        return;
+
     wxAuiToolBarItem* hitItem;
     hitItem = FindToolByPosition(evt.GetX(), evt.GetY());