zstd: Return if calloc is failed for zstd decompression contexts

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

Author: cosmo0920

src/flb_zstd.c

@@ -240,6 +240,7 @@ void *flb_zstd_decompression_context_create(void)
 
     if (context == NULL) {
         flb_errno();
+        return NULL;
     }
 
     context->dctx = ZSTD_createDCtx();