[Combo Chart] line and scatter chart event detecting bug

[jung-han]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'https://nhn.github.io/tui.chart/latest/tutorial-example08-04-combo-chart-line-and-scatter'
2. Uncheck Efficiency checkbox
3. Mouse on chart.
4. See error.

Expected behavior
Dots in the scatter chart do not appear.

Screenshots
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Desktop (please complete the following information):

• OS: All
• Browser All
• Version v3.9.0

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.