defensive toasts

Closes #1376

components/Editor.js

@@ -298,7 +298,7 @@ class Editor extends React.Component {
     this.context.snippet.update(this.props.snippet.id, this.state).then(() =>
       this.props.setToasts({
         type: 'SET',
-        toast: [{ children: 'Snippet saved', timeout: 3000 }],
+        toasts: [{ children: 'Snippet saved', timeout: 3000 }],
       })
     )
 

components/Toasts.js

@@ -94,11 +94,11 @@ function ToastContainer(props) {
   return (
     <div className="toast">
       {props.toasts
-        .slice()
-        .reverse()
-        .map(toast => (
-          <Toast key={toast.children} {...toast} />
-        ))}
+        ? props.toasts
+            .slice()
+            .reverse()
+            .map(toast => <Toast key={toast.children} {...toast} />)
+        : null}
       <style jsx>
         {`
           .toast {