btrfs-progs: fix conditions order when parsing scrub status line

As reported (cppcheck), the conditions are reversed as we first need to
check the limit and only then access the data.

Issue: #1030
Signed-off-by: David Sterba <[email protected]>

Author: kdave

cmds/scrub.c

@@ -663,7 +663,7 @@ static struct scrub_file_record **scrub_read_file(int fd, int report_errors)
 			++state;
 			fallthrough;
 		case 2: /* start of line, skip space */
-			while (isspace(l[i]) && i < avail) {
+			while (i < avail && isspace(l[i])) {
 				if (l[i] == '\n')
 					++lineno;
 				++i;