**Current behavior:**
In the mobile view for detailed operations of a picking (move lines), the user fills in each field individually instead of selecting a quant. If the quantity of some line is zero and is for a tracked product, the `lot_id` of the line will remain empty while they have encoded some quantity.

**Expected behavior:**
In this situation, if a quant for the tracked product is available it should be added on the line automatically.

**Steps to reproduce:**
1. In mobile, create a manufacturing order to build some product using a component which is tracked via lot

2. Open the MO in shop floor and click on the component line

3. Set the line's quantity to zero and clear the lot -> save

4. Re-open the line and encode some non-zero quantity -> save

5. Observe that the line has quantity but not a lot

**Cause of the issue:**
On mobile these fields are set individually versus desktop where an actual quant is selected to pull product from, thus this scenario was likely just overlooked.

**Fix:**
When writing a quantity on a line that previously had a quantity of zero for a tracked product, try to find an available lot to write to the line as well.

opw-3919816