tests: internal: multiline: Add a NULL assertion

Signed-off-by: Hiroshi Hatake <[email protected]>

Author: cosmo0920

tests/internal/multiline.c

@@ -1484,6 +1484,12 @@ static void test_buffer_limit_truncation()
 
     /* Use the dummy 'docker' parser for JSON extraction */
     p = flb_parser_get("docker", config);
+    TEST_CHECK(p != NULL);
+    if (!p) {
+        /* Built-in 'docker' parser unavailable in this build; skip gracefully */
+        flb_config_exit(config);
+        return;
+    }
 
     /* This parser will trigger on any content, ensuring concatenation. */
     ml = flb_ml_create(config, "limit-test");