in_process_exporter_metrics: Ensure hash key is valid before checking

Signed-off-by: Pierre-Yves Rofes <3604235+piwai@users.noreply.github.com>

Author: piwai

plugins/in_process_exporter_metrics/pe_process.c

@@ -992,10 +992,17 @@ static void purge_stale_metrics(struct cmt_map *map,
             }
             if (!key) {
                 key = flb_sds_create(label_val);
+                if (!key) {
+                    break;
+                }
             }
             else {
-                flb_sds_cat_safe(&key, "|", 1);
-                flb_sds_cat_safe(&key, label_val, strlen(label_val));
+                if (flb_sds_cat_safe(&key, "|", 1) == -1 ||
+                flb_sds_cat_safe(&key, label_val, strlen(label_val)) == -1) {
+                flb_sds_destroy(key);
+                key = NULL;
+                break;
+                }
             }
         }
         if (!key) {