Step over does not work well when debugging js code

Reproduction steps:
1. Create a Qt Quick application.
2. Add a js function in main.qml code and set two breakpoints see
qml.png.
3. Compile the qml debug library and check "Link qml Debugging Library".
4. Check qml debugger in run configuration.Debug Port:3768.
5. Start debugging.
6. When debugger stop at line 22 press F10 to step over. The debugger
stop at line15 which is unreasonable.