Blender Git Loki

Eevee: Fix conditional statement depending on unitialized value

Basically since g_data was malloc'ed (instead of calloc'ed)
g_data->minzbuffer was never initialized.

So when running DRW_framebuffer_init after EEVEE_effects_init, the test
to *g_data->minzbuffer would lead to unpredictable results.

This was caught by valgrind, reported by Sergey Sharybin.