patch 9.0.1344: check for OSC escape sequence doesn't work

Problem:    Check for OSC escape sequence doesn't work.
Solution:   Fix typo in index.
diff --git a/src/term.c b/src/term.c
index ab1ad57..2f0a0cb 100644
--- a/src/term.c
+++ b/src/term.c
@@ -5716,7 +5716,7 @@
 
 		if (i - j >= 15 && STRNCMP(tp + j + 3, "rgb:", 4) == 0
 			    && (is_4digit
-				   || (tp[j + 9] == '/' && tp[i + 12] == '/')))
+				   || (tp[j + 9] == '/' && tp[j + 12] == '/')))
 		{
 		    char_u *tp_r = tp + j + 7;
 		    char_u *tp_g = tp + j + (is_4digit ? 12 : 10);