Fix wxCommandProcessor::IsDirty() for unsaved unmodified case.

IsDirty() still returned true even after undoing all the commands which was
wrong, as there was nothing to save in this case.

Closes #15722.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75310 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/cmdproc.cpp

@@ -329,16 +329,11 @@ void wxCommandProcessor::ClearCommands()
 
 bool wxCommandProcessor::IsDirty() const
 {
-    if ( m_commands.empty() )
-    {
-        // If we have never been modified, we can't be dirty.
-        return false;
-    }
-
     if ( !m_lastSavedCommand )
     {
-        // If we have been modified but have never been saved, we're dirty.
-        return true;
+        // We have never been saved, so we are dirty if and only if we have any
+        // commands at all.
+        return m_currentCommand;
     }
 
     if ( !m_currentCommand )