patch 9.0.1132: code is indented more than needed

Problem:    Code is indented more than needed.
Solution:   Use an early return to reduce indentation. (Yegappan Lakshmanan,
            closes #11769)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 4884ebd..49331c4 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -4210,11 +4210,11 @@
 {
     rettv->v_type = VAR_STRING;
     rettv->vval.v_string = alloc(2);
-    if (rettv->vval.v_string != NULL)
-    {
-	rettv->vval.v_string[0] = get_cmdline_type();
-	rettv->vval.v_string[1] = NUL;
-    }
+    if (rettv->vval.v_string == NULL)
+	return;
+
+    rettv->vval.v_string[0] = get_cmdline_type();
+    rettv->vval.v_string[1] = NUL;
 }
 
 // Set the command line str to "str".