YAML checker fails to detect incorrect angles path in loader config

The following minimal example of a DIAD loader incorrectly configured (the path for the angles should be `/entry/imaging_sum/gts_theta_value`):
```yaml
- method: standard_tomo
module_path: httomo.data.hdf.loaders
parameters:
name: tomo
data_path: /entry/imaging/data
image_key_path: /entry/instrument/imaging/image_key
rotation_angles:
data_path: /entry/imaging_sum/gts_theta_val
```
reproduces the bug, where the pipeline doesn't raise any errors but it should:
```
(/dls/science/users/twi18192/conda-envs/httomo) [twi18192@pc0074 httomo (feature/padded-dataset-store)]$ python -m httomo check incorrect-angles-not-detected.yaml tests/test_data/k11_diad/k11-18014.nxs
Checking that the YAML_CONFIG is properly indented and has valid mappings and tags...
Sanity check of the YAML_CONFIG was successfully done...

Checking that the first method in the pipeline is a loader...
Loader check successful!!

Checking that the paths to the data and keys in the YAML_CONFIG file match the paths and keys in the input file (IN_DATA)...
Loader paths check successful!!

Validation of pipeline YAML file is successful.
```