Allow search against null values

[shawnwall]

• only search against non-null values to prevent search crash when searching null
• update to story data and generator for null test case
• noting that when sorting, the row will drop to the end of the result set

Let me know if there's anything else I can provide or help with here

Fixes https://github.com/imballinst/react-bs-datatable/issues/140

[imballinst]

hey @shawnwall, thanks for creating the issue and for contributing with this PR! I really appreciate it.

Could you help update this part? It seems this part of the code causes the build to fail:

[build:*docs] Error: src/stories/00-Uncontrolled.stories.tsx:168:25 - error TS2322: Type '({ name: string; username: string; date: string; score: number; location: string; status: string; } | { name: string; username: string; date: string; score: number; location: null; status: string; })[]' is not assignable to type 'StoryColumnType[]'.

Perhaps the update is just changing the location from string to string | null and then we should be good to merge this. Thanks!

[shawnwall]

updated with your suggestion, and a local yarn build ran successfully.