Using plug-ins to report errors Cannot read property 'getCode' of undefined

**Describe the bug**

**To Reproduce**

Minimal code to reproduce the bug

```js
const {
production,
} = require('./config/index');

const date = {
presets: [
[
'@babel/preset-env',
{
useBuiltIns: 'usage',
},
],
'@babel/preset-typescript',
],
plugins: ['@babel/proposal-class-properties', '@babel/proposal-object-rest-spread'],
};
if (production) {
date.presets.push('minify');
date.plugins.push('transform-remove-console', 'transform-remove-debugger',
'minify-dead-code-elimination', 'minify-guarded-expressions', 'minify-mangle-names',
'minify-replace', 'minify-simplify', 'transform-undefined-to-void', 'minify-type-constructors',
'transform-merge-sibling-variables', 'transform-minify-booleans');
}

module.exports = date;

```

**Actual Output**

If there is no Error thrown,

```js
Module build failed (from ./node_modules/happypack/loader.js):
TypeError: Cannot read property 'getCode' of undefined
at NodePath.getSource (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\path\introspection.js:164:27)
at PluginPass.Program (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\babel-plugin-minify-simplify\lib\index.js:490:41)
at newFn (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\visitors.js:193:21)
at NodePath._call (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\path\context.js:53:20)
at NodePath.call (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\path\context.js:40:17)
at NodePath.visit (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\path\context.js:88:12)
at TraversalContext.visitQueue (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\context.js:118:16)
at TraversalContext.visitSingle (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\context.js:90:19)
at TraversalContext.visit (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\context.js:146:19)
at Function.traverse.node (C:\Users\Administrator\Desktop\WebPackMultiPageConfiguration\node_modules\@babel\traverse\lib\index.js:94:17)
npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! configure@1.0.0 build: `cross-env NODE_ENV=production webpack --config build/webpack.prod.js`
npm ERR! Exit status 2
npm ERR!
npm ERR! Failed at the configure@1.0.0 build script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
```

**Expected Output**

```js
Successful output
```

**Stack Trace**

If applicable,

```

```

**Configuration**

How are you using babel-minify?

`webpack4`

babel-minify version: `0.4.3`

babel version : `7.0.0-beta.49`

babel-minify-config:

```json5
{
removeConsole: true,
keepFnNames: true
}
```

babelrc:

```json5
{
plugins: [],
presets: []
}
```

**Possible solution**

**Additional context**

Reproduce the webpack4 build with babel-minify 0.4.3 and Babel 7.0.0-beta.49, then inspect babel-plugin-minify-simplify/lib/index.js around PluginPass.Program and the NodePath.getSource stack frame in @babel/traverse/lib/path/introspection.js. Done means the build no longer throws the getCode error and produces successful output.

Written by the indexing model from the issue text.