patch 8.2.0334: abort called when using test_void()

Problem:    Abort called when using test_void(). (Dominique Pelle)
Solution:   Only give an error, don't abort.
diff --git a/src/json.c b/src/json.c
index d5e5782..f4a03e6 100644
--- a/src/json.c
+++ b/src/json.c
@@ -352,7 +352,7 @@
 #endif
 	case VAR_UNKNOWN:
 	case VAR_VOID:
-	    internal_error("json_encode_item()");
+	    internal_error_no_abort("json_encode_item()");
 	    return FAIL;
     }
     return OK;