Revert "iniialize global bottom explizit with NULL"

This reverts commit 0734cb7680bed852a4fed4ca8eced9ad9b69c53f.

scroll.c

@@ -49,7 +49,7 @@ struct line {
 	size_t size;
 	size_t len;
 	char *buf;
-} *bottom = NULL;
+} *bottom;
 
 pid_t child;
 int mfd;