Invalid Mapping

I'm getting this error when trying to run danger (both 'danger pr' and 'danger ci'):

```
Error: { Error: dangerfile.js: Invalid mapping: {"generated":{"line":3,"column":0},"source":null,"original":{"line":1,"column":0}}
at SourceMapGenerator_validateMapping [as _validateMapping] (/Users/adarlocker/Documents/gefen/node_modules/source-map/lib/source-map-generator.js:289:13)
at SourceMapGenerator_addMapping [as addMapping] (/Users/adarlocker/Documents/gefen/node_modules/source-map/lib/source-map-generator.js:101:16)
at Array.forEach ()
at SourceMap.get (/Users/adarlocker/Documents/gefen/node_modules/babel-generator/lib/source-map.js:49:25)
at Object.get [as map] (/Users/adarlocker/Documents/gefen/node_modules/babel-generator/lib/buffer.js:53:33)
at File.generate (/Users/adarlocker/Documents/gefen/node_modules/babel-core/lib/transformation/file/index.js:710:26)
at File.transform (/Users/adarlocker/Documents/gefen/node_modules/babel-core/lib/transformation/file/index.js:554:17)
at /Users/adarlocker/Documents/gefen/node_modules/babel-core/lib/transformation/pipeline.js:50:19
at File.wrap (/Users/adarlocker/Documents/gefen/node_modules/babel-core/lib/transformation/file/index.js:564:16)
at Pipeline.transform (/Users/adarlocker/Documents/gefen
```

The only solution I could find for now (and only locally) is commenting the relevant lines inside node_modules (bolded):

```
SourceMapGenerator.prototype.addMapping =
function SourceMapGenerator_addMapping(aArgs) {
var generated = util.getArg(aArgs, 'generated');
var original = util.getArg(aArgs, 'original', null);
var source = util.getArg(aArgs, 'source', null);
var name = util.getArg(aArgs, 'name', null);

**// if (!this._skipValidation) {
// this._validateMapping(generated, original, source, name);
// }**

if (source != null) {
source = String(source);
if (!this._sources.has(source)) {
this._sources.add(source);
}
}

if (name != null) {
name = String(name);
if (!this._names.has(name)) {
this._names.add(name);
}
}

this._mappings.add({
generatedLine: generated.line,
generatedColumn: generated.column,
originalLine: original != null && original.line,
originalColumn: original != null && original.column,
source: source,
name: name
});
};
```
Any suggestions? Is it a known issue? I couldn't find any open issue related.

Start by reproducing the error with `danger pr` and `danger ci`, then read `dangerfile.js` and the stack-trace entry points `node_modules/source-map/lib/source-map-generator.js` and `node_modules/babel-generator/lib/source-map.js`. Trace the invalid mapping and verify that both commands complete without the error.

Written by the indexing model from the issue text.