Doesn't seem to be able to debug contracts with private mapping.

> Please provide us with the following information:
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### This issue is for a: (mark with an `x`)
```
- [ x] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
>
Add a state variable "mapping(uint256 => address) internal a_map;"
Then, add "a_map[1] = msg.sender;" in any function and execute and debug that function.

### Any log messages given by the failure
>
None
### Expected/desired behavior
>
The debugger to work, when debug starts, it just stays at the entry point of the program, F10 does not do anything.

### OS and Version?
> Windows 7, 8 or 10. Linux (which distribution). macOS (Yosemite? El Capitan? Sierra?)
Window 10
### Versions
>
Newest.
### Mention any other details that might be useful

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