user32!RegisterClassExA accessing class name without NULL check

Software tested: Code CrearVentana.c Binary CrearVentana.exe

ReactOS Master: 0.4.15-dev-6024-g27c0f0e-x86-gcc-lin-dbg
CD: Bootcd
Compiler: GCC Only
Arch: 32 bits.

Description:
I will explain a bug now that I don't know if deserves a ticket. Let's say, I'm not sure where is the failure itself.
I have a binary compiled with the ReactOS Build Environment 2.2.1 (including the bin folder in path) with a "faulty code" (compilable but pointless, the window lpsz class is defined as NULL). It must open as a window with a MB_ERROR as it does under Wine or Windows XP. I know it's a mistake.

But it doesn't, the binary starts under ReactOS, but in the case of RosBE compiled it shows me a memory read error:

Curiously, if I compile the software using CodeBlocks with the MinGW compiler (available under RAPPS), the issue dissapears (because it uses another version of gcc or g++ that workaround the issue?).

Anyway the previous binary (attached too), must execute as Windows XP, isn't it?

Steps to reproduce:
1. Install RosBE under ReactOS.
2. Compile the binary using RosBE with "gcc -o CrearVentana.exe CrearVentana.c"
3. Execute the CrearVentana.exe

Log: CrearVentanaBug2.log