This patch fixes a bug in the original driver: write to NULL descriptor.

b/182179434

--- a/src/wrapper.c
+++ b/src/wrapper.c
@@ -244,6 +244,10 @@ main (int argc, char *argv[])
 				break;
 			}
 
+			if(pfp == NULL){ // do not write anything if pipe is not open
+				break;
+			}
+
 			if(first_fwrite){//最初のfwriteだけ、ページ数を送信
 				fwrite (&pageNum, 1, 1, pfp);
 				first_fwrite = FALSE;
@@ -404,7 +408,9 @@ main (int argc, char *argv[])
 	free (page_raw);
 	free (page_raw_cache);
 
-	pclose (pfp);
+	if(pfp != NULL){
+		pclose (pfp);
+	}
 	cupsRasterClose (ras);
 
 	return 0;