text: normalize the indentation in do_indent() and do_unindent()

Also remove one unneeded blank line.

src/text.c

@@ -403,7 +403,6 @@ void do_unindent(ssize_t cols)
     for (f = top; f != bot->next; f = f->next) {
 	size_t line_len = strlen(f->data);
 	size_t indent_len = indent_length(f->data);
-
 	size_t indent_col = strnlenpt(f->data, indent_len);
 		/* The length in columns of the indentation on this line. */