Fix rowPixelSpacing to not be null (#321)
Fix rowPixelSpacing to not be null (#321)

In cases where image.rowPixelSpacing is null, it will be assigned null to rowPixelSpacing and logic will fail. I.e. rowPixelSpacing must be a number and different from 0
chafey/cornerstone,chafey/cornerstone,cornerstonejs/cornerstone,cornerstonejs/cornerstone,cornerstonejs/cornerstone,cornerstonejs/cornerstone