Devtools Debugger allows setting phantom breakpoints

Clicking on blank space that precedes the line with the code indicates it sets a breakpoint on that line of code, but it is not being actually triggered.
See the video below at second 6:
[cast.webm](https://github.com/flutter/devtools/assets/381137/de50fbc2-f2a1-46ac-bc46-a9465f982bf6)

Reproduce the behavior in the DevTools Debugger using the linked recording, focusing on clicking blank space before a line of code. Trace how that click creates and reports a breakpoint, then verify that the phantom breakpoint is no longer shown as set or is triggered correctly.

Scritto dal modello di indicizzazione a partire dal testo della issue.