Fix undefined controller error in tooltip plugin

[DrowningElysium]

Issue that has been made clear in #11596 (comment)

Issue also applies to a project of mine where the data is loaded twice, (Once from local storage and once from a result from a request), which might cause the issue.

[LeeLenaleee]

@etimberg we dissalowed optional chaining because it was not stable yet and not all platforms supported it. It seems it is stable now and every major browser supports it, except for IE 11 but we do not support that ourselfs.

I think we can use it now, what is your oppnion on it?
https://caniuse.com/?search=optional%20chaining

[etimberg]

@LeeLenaleee I'm ok to use it now that it's stable

[aStarlikeMine]

I have this exact issue currently and will wait for this fix to be merged.

Our scenario happens when swopping between the graph on the dashboard and the page load from the graph click event multiple times, and only when this is done quickly.

[daviddeutsch]

Just confirming that I also have this issue in my current codebase - in my case, it seems to be related to multiple graphs being loaded at the same time under a stress test. It's four graphs in total with four sets of data (~600 points) being drawn each.

I've already staggered the loading because it wouldn't go smoothly otherwise (I first init the graphjs instance and then load in the data a short timeout later) and the missing controller happens seemingly at random - skipping over the error, all tooltips work just fine a moment later, navigating away and back to the page, I cannot reproduce the error consistently.

Another weird thing is that when I add a breakpoint to where the error occurs, I can print out the content of controller just fine (it's not null), but then the error happens anyhow (it reports that controller IS null).

I first thought that the fix in this PR resolved the issue, but the error ended up cropping up again, so now I'm completely unsure what causes it.

[Imran-imtiaz48]

Changes Made:

• Modified the code to use optional chaining (?.) in place of direct property access (.) for getParsed method of controller.

Review:

1. Clarity and Intent:

   • The change enhances code clarity by adopting optional chaining (?.), which ensures that the code gracefully handles cases where controller might be null or undefined.
   • This approach improves robustness and reduces the likelihood of TypeError exceptions when accessing properties of potentially null objects.

2. Impact on Functionality:

   • Functionally, the modification preserves the original behavior of filtering lastActive elements based on the validity check of active elements.
   • By using optional chaining, the code remains concise without compromising on its intended functionality.

3. Code Readability:

   • The revised code maintains readability by adhering to modern JavaScript practices. It effectively communicates the intention of guarding against potential undefined values in a clear and succinct manner.

4. Compatibility and Best Practices:

   • Optional chaining is a recommended approach in ECMAScript 2020 (ES11) and later, promoting better code maintainability and compatibility across different JavaScript environments.

Conclusion:
The proposed change is well-executed and aligns with best practices for modern JavaScript development. It enhances code reliability and readability without introducing unnecessary complexity.

Recommendation:
Merge the pull request after ensuring that all tests related to this functionality pass successfully.