wasm: uri fetch triggers a crash

When configured with `uri` fetch, Wasm HTTP filter sometimes triggers a crash:
```
(redacted)
2023-01-11T23:38:04.086902Z warning envoy wasm createWasm: failed to load (in progress)
2023-01-11T23:38:04.086942Z warning envoy wasm createWasm: failed to load (cached)
2023-01-11T23:38:07.882552Z critical envoy backtrace Caught Segmentation fault, suspect faulting address 0x8
2023-01-11T23:38:07.882594Z critical envoy backtrace Backtrace (use tools/stack_decode.py to get line numbers):
2023-01-11T23:38:07.882597Z critical envoy backtrace Envoy version: 4d99fb094f34379565ba63c5a0bb19d86c8d7447/1.23.4-dev/Modified/RELEASE/BoringSSL-FIPS
2023-01-11T23:38:07.882996Z critical envoy backtrace #0: [0x7f90ee624520]
2023-01-11T23:38:07.893044Z critical envoy backtrace #1: std::__1::__function::__func<>::operator()() [0x12bbe8b]
2023-01-11T23:38:07.903881Z critical envoy backtrace #2: Envoy::Http::FilterManager::applyFilterFactoryCb() [0x27884d6]
2023-01-11T23:38:07.913225Z critical envoy backtrace #3: Envoy::Extensions::NetworkFilters::HttpConnectionManager::HttpConnectionManagerConfig::createFilterChainForFactories() [0x27558bf]
```