Fix bug with pre-fetching noise in cases of only a single target

[codecov[bot]]

Codecov Report

Base: 94.79% // Head: 94.75% // Decreases project coverage by -0.04% :warning:

Coverage data is based on head (aceea70) compared to base (e5955f6). Patch coverage: 86.66% of modified lines in pull request are covered.

Additional details and impacted files

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[sdhiscocks]

In the scenario len(ground_truths) == 1 and noise == True (which happens in the Disjoint_Tracking_Classification.py example) Then measurement_noise = True Which doesn't cause an error on the line measurement_vector += measurement_noise It just adds 1 to the measurement_vector

Would this be a suitable solution:

if noise is True:
    # Pre-fetch noise values when more than one target
    if len(ground_truths) > 1:
        noise_vectors_iter = iter(measurement_model.rvs(len(ground_truths), **kwargs))
    else:
        noise_vectors_iter = iter([measurement_model.rvs(**kwargs)])

Thanks @gawebb-dstl, I hadn't spotted that. I've updated it for sensors where this is an issue.

[gawebb-dstl]

@sdhiscocks I noticed you were having to rewrite the same code in many different places, so I tried to abstract that code to one class see #732