Number text fields in the structure block GUI don't restrict input to numbers only

The bug

The following text fields in the structure block GUI are supposed to only accept numbers:

• Relative Position (X, Y, Z)
• Structure Size (X, Y, Z)
• Structure Integrity
• Structure Seed

However, you're able to input any text in these fields, not only numbers. On saving the structure block, the text inputted into these fields will not be saved and convert to a number (usually 0).

To reproduce

1. Open structure block GUI
2. Switch to Save or Load mode
3. Put random words into any of the mentioned fields
4. That is possible