In SUBSCRIPTP (src/wxMathML.lisp), correct test for presence of wxxml…

…_subscripted in Maxima symbol properties.

Fixes bug report #1807: "The display of subscipts has been backsliding for long"
and bug report #1584: "Underscores not converted to subscripts"

src/wxMathML.lisp

@@ -368,7 +368,7 @@ Submit bug reports by following the 'New issue' link on that page."))
 			 ($get sub-symb '$wxxml_subscript)
 			 )
 		     (ignore-errors (not
-				     (member '$WXXML_SUBSCRIPTED (cadr (properties x))))))))
+				     (member '$WXXML_SUBSCRIPTED (cdr (properties x))))))))
 	  (format nil  "<munder altCopy=\"~A\"><mrow>~a</mrow><mrow>~a</mrow></munder>"
 		  (wxxml-alt-copy-text x)
 		  (format nil "<mi>~a</mi>" (wxxml-fix-string (format nil "~A" sub-var)))