out_vivo_exporter: fix regression on buffer check

Signed-off-by: Eduardo Silva <eduardo@chronosphere.io>

Author: edsiper

plugins/out_vivo_exporter/vivo.c

@@ -277,14 +277,18 @@ static flb_sds_t format_logs(struct flb_input_instance *src_ins,
 
     msgpack_sbuffer_destroy(&tmp_sbuf);
 
-    /* append a newline */
-    flb_sds_cat_safe(&out_js, "\n", 1);
-
     if (!out_js) {
         flb_sds_destroy(out_buf);
         return NULL;
     }
 
+    /* append a newline */
+    if (flb_sds_cat_safe(&out_js, "\n", 1) < 0) {
+        flb_sds_destroy(out_js);
+        flb_sds_destroy(out_buf);
+        return NULL;
+    }
+
     /* Replace out_buf with the complete JSON */
     flb_sds_destroy(out_buf);
     return out_js;