http: don't crash when normalizing uri on low memory

src/app-layer-htp-libhtp.c

@@ -201,12 +201,14 @@ bstr *SCHTPGenerateNormalizedUri(htp_tx_t *tx, htp_uri_t *uri, int uri_include_a
 
     if (uri->query != NULL) {
         bstr *query = bstr_dup(uri->query);
+        if (query) {
             uint64_t flags = 0;
             htp_urldecode_inplace(tx->cfg, HTP_DECODER_URLENCODED, query, &flags);
             bstr_add_c_noex(r, "?");
             bstr_add_noex(r, query);
             bstr_free(query);
         }
+    }
 
     if (uri->fragment != NULL) {
         bstr_add_c_noex(r, "#");