Cannot read property 'namespace' of null

[riophae]

eslint version: 5.2.0
eslint-plugin-import version: 2.13.0
Minimal reproduction: https://github.com/riophae/eslint-plugin-import-bug

Steps to reproduce:

git clone git@github.com:riophae/eslint-plugin-import-bug.git
cd eslint-plugin-import-bug
npm install
npm test

Got this:

[/mnt/d/Projects/eslint-plugin-import-bug]$ npm test

> eslint-plugin-import-bug@ test /mnt/d/Projects/eslint-plugin-import-bug
> eslint .

Cannot read property 'namespace' of null
TypeError: Cannot read property 'namespace' of null
    at testKey (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint-plugin-import/lib/rules/namespace.js:194:69)
    at VariableDeclarator (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint-plugin-import/lib/rules/namespace.js:199:9)
    at listeners.(anonymous function).forEach.listener (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/util/safe-emitter.js:45:58)
    at Array.forEach (<anonymous>)
    at Object.emit (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/util/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/util/node-event-generator.js:251:26)
    at NodeEventGenerator.applySelectors (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/util/node-event-generator.js:280:22)
    at NodeEventGenerator.enterNode (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/util/node-event-generator.js:294:14)
    at CodePathAnalyzer.enterNode (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/code-path-analysis/code-path-analyzer.js:632:23)
    at nodeQueue.forEach.traversalInfo (/mnt/d/Projects/eslint-plugin-import-bug/node_modules/eslint/lib/linter.js:860:28)
npm ERR! Test failed.  See above for more details.