patch 8.2.1991: Coverity warns for not using the ga_grow() return value

Problem:    Coverity warns for not using the ga_grow() return value.
Solution:   Bail out if ga_grow() fails. (Yegappan Lakshmanan, closes #7303)
diff --git a/src/getchar.c b/src/getchar.c
index 3d73a6c..165a6a3 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -3645,7 +3645,11 @@
     got_int = FALSE;
     while (c1 != NUL && !aborted)
     {
-	ga_grow(&line_ga, 32);
+	if (ga_grow(&line_ga, 32) != OK)
+	{
+	    aborted = TRUE;
+	    break;
+	}
 
 	if (vgetorpeek(FALSE) == NUL)
 	{