chart-UI graphing error if X-Axis data point limit > 50% of available data points

### Current Behavior

Charts appear to have a straight line joining the first and last datapoints if the X Axis limit value for points is more than half of the available points.

Graph above with database query returning 100 data points, and the X Axis limit set to 2 Days or 51 points.

Graph above with database query returning 100 data points, and the X Axis limit set to 2 Days or 50 points.

Graph above with database query returning 3200 data points, and the X Axis limit set to 2 Days or 1601 points.

Graph above with database query returning 3200 data points, and the X Axis limit set to 2 Days or 1600 points.

### Expected Behavior

Chart should not have a straight line joining the first and last datapoints unless there are only 2 datapoints.

### Steps To Reproduce

Write a query to generate some data from a database, in that query apply a limit of any figure.
On the chart X axis limit, set the Or number of datapoints to be (the query limit/2) +1
OR any point limit of more than half of the datapoints available

eg

Graph above with database query returning 100 data points, and the X Axis limit set to 2 Days or 51 points.

Graph above with database query returning 100 data points, and the X Axis limit set to 2 Days or 50 points.

Graph above with database query returning 3200 data points, and the X Axis limit set to 2 Days or 1601 points.

Graph above with database query returning 3200 data points, and the X Axis limit set to 2 Days or 1600 points.

### Environment

- Dashboard version:2.0 (1.16)
- Node-RED version:4.02
- Node.js version: v20.17.0
- npm version:10.8.2
- Platform/OS: Linux/Debian
- Browser: Firefox

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate