plugin: filter_multiline: Add a NULL check on initialize

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

Author: cosmo0920

plugins/filter_multiline/ml.c

@@ -382,6 +382,12 @@ static int cb_ml_init(struct flb_filter_instance *ins,
                                                 "fluentbit", "filter", "emit_truncated_total",
                                                 "Total number of truncated occurence of multiline",
                                                 1, (char *[]) {"name"});
+        if (!ctx->cmt_truncated) {
+            flb_errno();
+            flb_free(ctx);
+
+            return -1;
+        }
 
         /* OLD api */
         flb_metrics_add(FLB_MULTILINE_METRIC_TRUNCATED,