src: do not make Resize(0)’d buffers base nullptr

This fixes issues in which APIs that accept pointers created this way
treat `nullptr` and a zero-length buffer differently.
We already do something similar for our `Malloc()` implementation.

PR-URL: nodejs#26731
Fixes: nodejs#26514
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Michael Dawson <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>

Author: addaleax

src/env-inl.h

@@ -759,8 +759,10 @@ inline AllocatedBuffer::AllocatedBuffer(Environment* env, uv_buf_t buf)
     : env_(env), buffer_(buf) {}
 
 inline void AllocatedBuffer::Resize(size_t len) {
-  char* new_data = env_->Reallocate(buffer_.base, buffer_.len, len);
-  CHECK_IMPLIES(len > 0, new_data != nullptr);
+  // The `len` check is to make sure we don't end up with `nullptr` as our base.
+  char* new_data = env_->Reallocate(buffer_.base, buffer_.len,
+                                    len > 0 ? len : 1);
+  CHECK_NOT_NULL(new_data);
   buffer_ = uv_buf_init(new_data, len);
 }