redo() missing null guard that undo() has, will crash if no graph

[avinxshKD]

in toolbarFunctions.js around line 177:

const undo = (state) => {
    if (getGraphFun(state)) getGraphFun(state).undo();  // has guard
};
const redo = (state) => {
    getGraphFun(state).redo();  // no guard
};

undo checks if graph exists before calling .undo(), redo just yolos it. will throw if curGraphInstance is null/undefined. probably just copy-paste miss when these were written.

fix could be,,. add the same if (getGraphFun(state)) check