Use standard library style members of wxArrayString (and wxString) ...

... which will make it easier to change the types of those containers to
std::vectors of other string-like classes

for wxString,

IsEmpty => empty
Clear => clear
Alloc => reserve

for wxArrayString,

Count => size
GetCount => size
IsEmpty => empty
Add => push_back
Clear => clear
Empty => clear
Sort => std::sort (only with default comparator)
SetCount => resize
Last => back
Item => operator []
Alloc => reserve

src/AudacityException.cpp

@@ -97,7 +97,7 @@ void MessageBoxException::DelayedHandlerAction()
       if ( wxAtomicDec( sOutstandingMessages ) == 0 )
          ::AudacityMessageBox(
             ErrorMessage(),
-            caption.IsEmpty() ? AudacityMessageBoxCaptionStr() : caption,
+            caption.empty() ? AudacityMessageBoxCaptionStr() : caption,
             wxICON_ERROR
          );
       moved = true;