Return NULL if file doesnt open in deb_extract
diff --git a/libbb/unarchive.c b/libbb/unarchive.c
index 852bd06..d10e60c 100644
--- a/libbb/unarchive.c
+++ b/libbb/unarchive.c
@@ -568,7 +568,9 @@
 
 	/* open the debian package to be worked on */
 	deb_stream = wfopen(package_filename, "r");
-
+	if (deb_stream == NULL) {
+		return(NULL);
+	}
 	/* set the buffer size */
 	setvbuf(deb_stream, NULL, _IOFBF, 0x8000);