You cannot use CTRL+A to select all of the text in the sign GUI

The Bug:

You cannot use CTRL+A to select all of the text in the sign GUI.

Steps to Reproduce:

1. Obtain a sign and place it down.
2. Write something on it that goes across all four lines.
3. Press CTRL+A.
4. Take note as to whether or not you can use CTRL+A to select all of the text in the sign GUI.

Observed Behavior:

You only have the line that you're currently on selected, and not the entire text, therefore indicating that you cannot use CTRL+A to select all of the text in the sign GUI.

Expected Behavior:

You would be able to use CTRL+A to select all of the text in the sign GUI.