unreasonable values of `cl_cpos2lbound()` and `cl_cpos2rbound()` of `cpos` is outside strut

This is not yet a fully reproducible example, but consider this.

```r
get_region_matrix(corpus = "GERMAPARL2", s_attribute = "ne", strucs = 0:10)
```

```r
RcppCWB::cl_cpos2lbound(corpus = "GERMAPARL2", s_attribute = "ne", cpos = 111)
```
[1] 8

```r
RcppCWB::cl_cpos2rbound(corpus = "GERMAPARL2", s_attribute = "ne", cpos = 111)
```
[1] 170374808

I am using GermaParl v2.0.0.