Exception handling doesn't work

Given code like this where the file doesn't exist:

```
try {
    PhysFS::ifstream file ("filename.txt");
} catch (std::invalid_argument e) {
    //do something here
}
```

A bad access error will crash the program.

If I remove the exception handling, then it correctly shows the unhanded exception of:

```
throw std::invalid_argument("file not found: " + std::string(filename));
```
