numpy.linalg.LinAlgError when calling transform about staintools HOT 2 OPEN

tissue_mask = LuminosityThresholdTissueLocator.get_tissue_mask(I, luminosity_threshold=luminosity_threshold).reshape((-1,))
        OD = convert_RGB_to_OD(I).reshape((-1, 3))
        OD = OD[tissue_mask]


        # Yoni's edit!!
        if tissue_mask.sum() <= 1: # If the tissue mask has 0 or 1 pixel the linalg does not work. We will return an untransformed image
            return False

        # Eigenvectors of cov in OD space (orthogonal as cov symmetric)
        _, V = np.linalg.eigh(np.cov(OD, rowvar=False))

def transform(self, I, filename=''):
        """
        Transform an image.

        :param I: Image RGB uint8.
        :return:
        """
        stain_matrix_source = self.extractor.get_stain_matrix(I)

        # Yoni's edit: get_strain_matrix returns false if the linalg doesn't work out. If that doesn't work out, we return an untransformed image
        if isinstance(stain_matrix_source, np.ndarray):
            source_concentrations = get_concentrations(I, stain_matrix_source, multiThread=False)
            maxC_source = np.percentile(source_concentrations, 99, axis=0).reshape((1, 2))
            source_concentrations *= (self.maxC_target / maxC_source)
            tmp = 255 * np.exp(-1 * np.dot(source_concentrations, self.stain_matrix_target))
            return tmp.reshape(I.shape).astype(np.uint8)
        else:
            print(f"=== This image was seen as background by Macenko method, and is therefore not transformed: {filename}")
            return I.astype(np.uint8)