Flint and steel can be used on a water and lava block (source and flowing) to drain its durability

Summary:
When using flint & steel on a block that is filled with water or lava, its durability will be used up.

Steps to Reproduce:

1. Obtain a flint and steel
2. Switch to Survival mode
3. Use the flint and steel on a block filled with water or lava

Observed Results:
The flint and steel loses durability.

Expected Results:
The flint and steel should not lose durability.