patch 9.0.1460: insufficient testing for getcmdcompltype()

Problem:    Insufficient testing for getcmdcompltype().
Solution:   Add a few more test cases. (closes #12268)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 36d148e..21447ff 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -4152,11 +4152,11 @@
     if (p == NULL || p->xpc == NULL)
 	return NULL;
 
-    char_u *cmd_compl;
-
     set_expand_context(p->xpc);
+    if (p->xpc->xp_context == EXPAND_UNSUCCESSFUL)
+	return NULL;
 
-    cmd_compl = cmdcomplete_type_to_str(p->xpc->xp_context);
+    char_u *cmd_compl = cmdcomplete_type_to_str(p->xpc->xp_context);
     if (cmd_compl != NULL)
 	return vim_strsave(cmd_compl);