[I] [Bug] `echarts.connect` - Tooltip is not shown on connected chart if y-axis value is `NaN` [echarts]

["fpiemontese-dku (via GitHub)" <gi...@apache.org>]

fpiemontese-dku opened a new issue, #20607:
URL: https://github.com/apache/echarts/issues/20607

   ### Version
   
   5.5.0
   
   ### Link to Minimal Reproduction
   
   https://codepen.io/Francesco-Piemontese-the-sasster/pen/RNbpdJr
   
   ### Steps to Reproduce
   
   The attached CodePen should be all you need in order to reproduce - it's just two very basic line charts, with identical data on the x axis, connected via `echarts.connect`. The only peculiarity that some of the y-axis data points are `NaN`.
   
   To trigger the tooltip behaviour in question, simply hover either of the charts on an x-axis value for which the _other_ chart's y-axis value is `NaN`.
   
   ### Current Behavior
   
   When the `yAxis` data is not `NaN` in both charts, both tooltips are displayed (as expected), and their position is correctly synced.
   
   <img width="582" alt="image" src="https://github.com/user-attachments/assets/d5a15ed6-c71c-4b60-8c7a-2a74e32bb81e" />
   
   If, however, in the top chart I hover a datapoint for which the bottom chart has a `NaN` value, only the tooltip for the top chart is shown. 
   
   <img width="607" alt="image" src="https://github.com/user-attachments/assets/d0e27c25-9a79-4a81-a53a-bbb7f5483524" />
   
   This is despite the fact that the top chart's tooltip is also displayed for NaN values.
   
   <img width="588" alt="image" src="https://github.com/user-attachments/assets/74609734-5821-4009-9dec-1bb1a8a50f8d" />
   
   
   
   
   
   ### Expected Behavior
   
   The expected tooltip for each datapoint is shown on both charts, even if the datapoint being hovered is `NaN`
   
   ### Environment
   
   ```markdown
   Originally experienced this working in Angular 18 (both Chrome and Firefox), but could reproduce this in the plain JS environment of CodePen
   ```
   
   
   ### Any additional comments?
   
   Thank you so much for your help! 💚 


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