IndexError in .matrix when all scores are 0

[tornikeo]

Using .matrix of any similarity, when none of the scores are > 0, gets us an index error. Specifically:

from matchms.similarity import CosineGreedy
from ..builder_Spectrum import SpectrumBuilder

builder = SpectrumBuilder()
spectrum_1 = builder.with_mz(np.array([100, 200, 300], dtype="float")).with_intensities(
    np.array([0.1, 0.2, 1.0], dtype="float")).build()

spectrum_2 = builder.with_mz(np.array([50, 60, 70], dtype="float")).with_intensities(
    np.array([0.5, 0.2, 1.0], dtype="float")).build()

scores = CosineGreedy().matrix([spectrum_1], [spectrum_2]) # IndexError

Will give an index error. This PR adds testcase, and a fix for this.