[Bug-Candidate]: Infinite loop in `SlitherCompilationUnitSolc._analyze_using_for`

### Describe the issue:

While parsing https://etherscan.deth.net/address/0xb78d0db9cca422313a83eb368ca3d9f443433081 Slither falls info an infinite loop in `_analyze_using_for(...)`, repeatedly adding the same contract to `contracts_to_be_analyzed`.

### Code example to reproduce the issue:

```
$ slither 0xb78d0db9cca422313a83eb368ca3d9f443433081 --etherscan-apikey ...
```

### Version:

0.11.3

### Relevant log output:

```shell

```

Run the reported Slither command against the Etherscan address using version 0.11.3, then inspect SlitherCompilationUnitSolc._analyze_using_for and the contracts_to_be_analyzed behavior. Confirm the repeated contract additions and verify that analysis terminates without entering an infinite loop.

Written by the indexing model from the issue text.