BuildMesh Error

Hello,
I’m encountering a problem when using the buildmesh function in FreeFem++, which is causing a bug during execution. Additionally, I tried to use a try-catch block to handle the error, but it doesn’t seem to work as expected.
Could anyone help me understand why this issue occurs with buildmesh, and why the try-catch block is not able to catch the error?
Thanks in advance for your help!
try {
Th = buildmesh(bound0(-meshsize1) + bound1(meshsize1) + bound2(meshsize1) + bound3(meshsize1) + bound4(meshsize2) + bound5(meshsize2));
} The error message states that some vertices are missing, but since this is an error, I expected it to be caught by the catch block. However, the code does not seem to move into the catch block when the error occurs.