patch 9.0.1251: checking returned value of ga_grow() is inconsistent

Problem:    Checking returned value of ga_grow() is inconsistent.
Solution:   Check for FAIL instaed of "not OK". (Yegappan Lakshmanan,
            closes #11897)
diff --git a/src/getchar.c b/src/getchar.c
index f4dce02..2d30d4f 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -3890,7 +3890,7 @@
     got_int = FALSE;
     while (c1 != NUL && !aborted)
     {
-	if (ga_grow(&line_ga, 32) != OK)
+	if (ga_grow(&line_ga, 32) == FAIL)
 	{
 	    aborted = TRUE;
 	    break;