TypeError: Cannot read property 'innerBlocks' of null
    at InnerBlocks.synchronizeBlocksWithTemplate (script.build.js?ver=1:149405)
    at InnerBlocks.componentDidMount (script.build.js?ver=1:149366)
    at zc (react-dom.min.js?ver=16.6.3:146)
    at wc (react-dom.min.js?ver=16.6.3:138)
    at fa (react-dom.min.js?ver=16.6.3:137)
    at ng (react-dom.min.js?ver=16.6.3:149)
    at Se (react-dom.min.js?ver=16.6.3:40)

const {registerBlockType} = wp.blocks;
const {InspectorControls, RichText, MediaUpload} = wp.editor;

import {TextControl} from '@wordpress/components';

import {InnerBlocks} from '@wordpress/editor';

let blockStyle = {
    marginTop: "25px",
    marginBottom: "25px;"
};

registerBlockType('myself/test-component', {
    title: 'Test component',
    icon: 'editor-insertmore',
    category: 'common',
    attributes: {
        title: {
            type: 'string'
        }
    },

    edit(props) {
        const {setAttributes, attributes} = props;

        function setTitle(changes) {
            setAttributes({
                title: changes
            })
        }

        return (
            <div style={blockStyle}>
                <TextControl
                    placeholder="Titel"
                    value={attributes.title}
                    onChange={setTitle}
                />
                <InnerBlocks
                    templateLock={false}
                    renderAppender={(
                        () => <InnerBlocks.ButtonBlockAppender/>
                    )}
                />
            </div>
        )
    },

    save(props) {
        const {attributes, className} = props;

        return (
            <div style={blockStyle}>
                <InnerBlocks.Content/>
            </div>
        );
    }
});

key: "componentDidMount",
value: function componentDidMount() {
  var innerBlocks = this.props.block.innerBlocks; // only synchronize innerBlocks with template if innerBlocks are empty or a locking all exists

  if (innerBlocks.length === 0 || this.getTemplateLock() === 'all') {
    this.synchronizeBlocksWithTemplate();
  }

  if (this.state.templateInProcess) {
    this.setState({
      templateInProcess: false
    });
  }
}