pdfrenderer.cpp: Ignore non-text blocks
pdfrenderer.cpp: Ignore non-text blocks

Fix #3957.

tesseract-ocr/tesseract,amitdo/tesseract,amitdo/tesseract,amitdo/tesseract,amitdo/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract