Storybook exited with code 1

[vladninja]

Hi. I found 1 issue related to the preset (presetArgs).

If we are looking for an example of presetArgs: https://github.com/area17/blast#presetting-data all type of values are strings, and works well.
If in the example (in file stories/data/card.php) we change a title value to null, we get an error, like:

[0] info => Using cached manager
[0] webpack built preview d42a76af114de80996eb in 7378ms
[0] ModuleBuildError: Module build failed (from ./node_modules/@storybook/server/dist/cjs/server/loader.js):
[0] TypeError: Cannot convert undefined or null to object
[0]     at Function.keys (<anonymous>)
[0]     at stringifyObject (/var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:108:16)
[0]     at /var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:110:21
[0]     at Array.map (<anonymous>)
[0]     at stringifyObject (/var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:109:47)
[0]     at /var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:98:14
[0]     at Array.map (<anonymous>)
[0]     at stringifyObject (/var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:97:31)
[0]     at /var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:110:21
[0]     at Array.map (<anonymous>)
[0]     at stringifyObject (/var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:109:47)
[0]     at /var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:110:21
[0]     at Array.map (<anonymous>)
[0]     at stringifyObject (/var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:109:47)
[0]     at stringifyStory (/var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:159:69)
[0]     at /var/www/html/vendor/area17/blast/node_modules/@storybook/server/dist/cjs/lib/compiler/stringifier.js:165:12
[0]     at processResult (/var/www/html/vendor/area17/blast/node_modules/webpack/lib/NormalModule.js:721:19)
[0]     at /var/www/html/vendor/area17/blast/node_modules/webpack/lib/NormalModule.js:827:5
[0]     at /var/www/html/vendor/area17/blast/node_modules/loader-runner/lib/LoaderRunner.js:399:11
[0]     at /var/www/html/vendor/area17/blast/node_modules/loader-runner/lib/LoaderRunner.js:251:18
[0]     at runSyncOrAsync (/var/www/html/vendor/area17/blast/node_modules/loader-runner/lib/LoaderRunner.js:156:3)
[0]     at iterateNormalLoaders (/var/www/html/vendor/area17/blast/node_modules/loader-runner/lib/LoaderRunner.js:250:2)
[0]     at Array.<anonymous> (/var/www/html/vendor/area17/blast/node_modules/loader-runner/lib/LoaderRunner.js:223:4)
[0]     at runCallbacks (/var/www/html/vendor/area17/blast/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:27:15)
[0]     at /var/www/html/vendor/area17/blast/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:200:4
[0]     at /var/www/html/vendor/area17/blast/node_modules/graceful-fs/graceful-fs.js:123:16
[0]     at FSReqCallback.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:63:3)
[0]
[0]
[0] WARN Broken build, fix the error above.
[0] WARN You may need to refresh the browser.
[0] start-storybook --quiet -s /var/www/html/public -p 6006 exited with code 1

The key phrase is:
TypeError: Cannot convert undefined or null to object

Is it possible to add a support for null values to Blast?
Thanks