Pandas do not spawn when bamboo jungle biome is too small

The bug

Pandas do not spawn when bamboo jungle biome is too small.

Steps to reproduce

1. Create a Default world:

   Seed: 2917133137276911148
   X: 5312 Y: 110 Z: 5371
   

2. Use the following command to apply the effect to nearby pandas:

   /effect give @e[type=panda] glowing 1000