If I "Trim Both" a pair of lines which already meet, then neither line changes appearance on screen (as expected). However, after saving and reloading the file, both lines are now missing.

To reproduce:

1. Create a new drawing
2. Draw a 10x10 square
3. Save the drawing
4. Close and reopen. The square shows up as expected.
5. Use the Trim Both tool on a pair of lines meeting at one of the corners. No change in the display.
6. Save the drawing
7. Close and reopen. The lines used in step 5. have disappeared.

If one or both of the lines changes length, either lengthened or shortened, then the changed line is preserved.

Build information:

Version: 3.4.2.0 (3.4.2)
Build Date: Oct 25 2013
Qt Version: 4.7.4
Compiler: MSVC++ 10.0 (2010)

Running on Windows 7 64-bit.