Fix memory leak for PNG images
Fix memory leak for PNG images

Commit 5fe1390748a15c0e445a5c57c834edff27ff2f4d used an implementation
which created a new Pix object. That object was never destroyed.

Signed-off-by: Stefan Weil <8d4c780fcfdc41841e5070f4c43da8958ba6aec0@weilnetz.de>

jbarlow83/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,jbarlow83/tesseract,amitdo/tesseract,jbarlow83/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,UB-Mannheim/tesseract,tesseract-ocr/tesseract,UB-Mannheim/tesseract,jbarlow83/tesseract,stweil/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,jbarlow83/tesseract,stweil/tesseract,UB-Mannheim/tesseract,stweil/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract