Number Knob throws error when clearing value

[amcdnl]

Issue

When using knobs with Angular, when I created a number knob and then removed the value in the ui it throws the following error:

manager.bundle.js:6680 Warning: Received NaN for the `value` attribute. If this is expected, cast the value to a string.
    in input (created by NumberType)
    in NumberType (created by PropField)
    in div (created by PropField)
    in PropField (created by propForm)

from this config:

storiesOf('Stepper', module)
    .add(
        'Basic Stepper',
        withNotes(docs)(() => ({
            component: BasicStepperComponent,
            props: {
                step: number('Step', 0)
            },
            moduleMetadata: {
                imports: [StepperModule]
            }
        }))
    );

Versions

        "@angular/common": "^5.1.3",
        "@angular/compiler": "^5.1.3",
        "@angular/core": "^5.1.3",
        "@angular/platform-browser": "^5.1.3",
        "@angular/platform-browser-dynamic": "^5.1.3",
        "@storybook/addon-actions": "^3.4.0-alpha.0",
        "@storybook/addon-knobs": "^3.4.0-alpha.0",
        "@storybook/addon-links": "^3.4.0-alpha.0",
        "@storybook/addon-notes": "^3.4.0-alpha.0",
        "@storybook/addon-options": "^3.4.0-alpha.0",
        "@storybook/angular": "^3.4.0-alpha.0",

[alterx]

This is a knobs issue not directly related to the Angular implementation. I just tested the cra kitchen sink app and this is also happening. We should fix this in the addon itself.

[Hypnosphi]

Looks like a duplicate of #2475, closing this one. Feel free to open a PR