Avoid harmless MSVC warning about implicit bool conversion

With WXWIN_COMPATIBILITY_3_0 set to 1, m_anyModified member of
wxPropertyGridPageState is an unsigned char, not bool, so don't convert it to
a bool implicitly.

src/propgrid/manager.cpp

@@ -1079,7 +1079,10 @@ bool wxPropertyGridManager::IsPageModified( size_t index ) const
 {
     wxCHECK_MSG( index < GetPageCount(), false, wxS("Invalid page index") );
 
-    return m_arrPages[index]->GetStatePtr()->m_anyModified;
+    if ( m_arrPages[index]->GetStatePtr()->m_anyModified )
+        return true;
+
+    return false;
 }
 
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