patch 9.0.2021: Coverity complains about change in charset

Problem:  Coverity complains about change in charset (after v9.0.2017)
Solution: check pointer t at index 0

closes: #13322

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/charset.c b/src/charset.c
index 50a81cc..bda3f91 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1348,7 +1348,7 @@
     if (wp->w_p_lbr && wp->w_p_wrap && wp->w_width != 0)
     {
 	char_u	*t = cts->cts_line;
-	while (VIM_ISBREAK((int)*t))
+	while (VIM_ISBREAK((int)t[0]))
 	    t++;
 	vcol_start = t - cts->cts_line;
     }