Unhandled exception: Cannot read property 'catch' of null inside non-template JSON files

[StephenWeatherford]

I get this when deleting and then re-adding one of the commas in a dependencies section in an extension package.json file.

TypeError: Cannot read property 'catch' of null
at AzureRMTools.onProvideSignatureHelp (c:\Repos\vscode-azurearmtools\src\AzureRMTools.ts:554:23)
at Object.provideSignatureHelp (c:\Repos\vscode-azurearmtools\src\AzureRMTools.ts:215:45)
at c:\Program Files (x86)\Microsoft VS Code\resources\app\out\vs\workbench\node\extensionHostProcess.js:635:403

private onProvideSignatureHelp(document: vscode.TextDocument, position: vscode.Position, token: vscode.CancellationToken): Promise<vscode.SignatureHelp> {
    let result: Promise<vscode.SignatureHelp> = null;

    this.logOnError(() => {
        const deploymentTemplate: DeploymentTemplate = this.getDeploymentTemplate(document);
        if (deploymentTemplate) {
            const context: PositionContext = deploymentTemplate.getContextFromDocumentLineAndColumnIndexes(position.line, position.character);

            result = context.signatureHelp.then((functionSignatureHelp: TLE.FunctionSignatureHelp) => {
                let signatureHelp: vscode.SignatureHelp = null;

                **if (functionSignatureHelp) {**

...
}

                return signatureHelp;
            });
        }
    });


    return result.catch((error: any) => {    <<< result can be null