Node.js render hangs when repeating request after glyph load failure

[kudlav]

Describe the bug

Platform: Node.js

Rendering a tile. When a request to an external glyph fails, render is cancelled and callback is called with an error (which is expected). Then, the render hangs up when requesting the same tile for the second time.

To Reproduce

Steps to reproduce the behavior:

1. Render tile with a glyph that cannot be fetched
2. Error is returned instead of a tile
3. Render the same tile again
4. Render process hangs

Expected behavior

An error should be returned even on the second try.

Code example

https://gist.github.com/kudlav/999d60086eaf206726680a0ea45f7ed5

Output

#1
Rendering...
Callbacking request for tiles/15/17697/11101.pbf
Callbacking request for fonts/external/0-255.pbf
MBGL_MESSAGE [ERROR]    Style: Failed to load glyph range 0-255 for font stack external: Unknown url
FAILED, err:  [Error: Unknown url]
#2
Rendering...

The second retry hangs even if the glyphs is available during the second retry.

Platform information (please complete the following information):

• Operating System: Ubuntu 22.04.5 LTS
• Platform (e.g. Node.js, Qt): Node.js v22.11.0 / Node.js v18.19.0
• Version: 6.0.0

Bug Analysis

1. First request flow:

   • renderStill -> onUpdate -> renderFrame -> createRenderTree returns nullptr
   • triggers glyph requests
   • glyph request fails
   • renderFinished called with error
   • Flow completes successfully

2. Second request flow:

   • renderStill -> onUpdate -> renderFrame -> createRenderTree returns nullptr
   • NodeRequest destructors called
   • Process hangs, no renderFinished called

After createRenderTree returns nullptr in second attempt, the normal error handling path is not triggered, preventing renderFinished from being called.