* If an exception happens, the massNumber is set to null.
* @see org.openscience.jchempaint.controller.IAtomBondEdits#setSymbol(org.openscience.cdk.interfaces.IAtom, java.lang.String)
*/
public void setSymbol(IAtom atom, String symbol) {
if (getUndoRedoFactory() != null && getUndoRedoHandler() != null) {
IUndoRedoable undoredo = getUndoRedoFactory()
.getChangeAtomSymbolEdit(atom, atom.getSymbol(), symbol,
"Change Atom Symbol to " + symbol, this);
getUndoRedoHandler().postEdit(undoredo);
}
if (atom instanceof IPseudoAtom) {