Fix some -Wmaybe-uninitialized warnings

Namely:
```
modules/basis_universal/register_types.cpp: In function 'Ref<Image> basis_universal_unpacker(const Vector<unsigned char>&)':
modules/basis_universal/register_types.cpp:266:15: warning: 'imgfmt' may be used uninitialized in this function [-Wmaybe-uninitialized]
  266 |  image->create(info.m_width, info.m_height, info.m_total_levels > 1, imgfmt, gpudata);
      |  ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
modules/basis_universal/register_types.cpp:255:39: warning: 'format' may be used uninitialized in this function [-Wmaybe-uninitialized]
  255 |    bool ret = tr.transcode_image_level(ptr, size, 0, i, dst + ofs, level.m_total_blocks - i, format);
      |               ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

```
servers/visual_server.cpp: In member function 'Error VisualServer::_surface_set_data(Array, uint32_t, uint32_t*, uint32_t, Vector<unsigned char>&, int, Vector<unsigned char>&, int, AABB&, Vector<AABB>&)':
servers/visual_server.cpp:636:15: warning: 'iw' may be used uninitialized in this function [-Wmaybe-uninitialized]
  636 |       copymem(&iw[i * 2], &v, 2);
      |               ^
```

```
core/image.cpp: In member function 'Error Image::generate_mipmap_roughness(Image::RoughnessChannel, const Ref<Image>&)':
core/image.cpp:1683:11: warning: 'roughness' may be used uninitialized in this function [-Wmaybe-uninitialized]
 1683 |     float roughness;
      |           ^~~~~~~~~
```

0 files changed, 0 insertions, 0 deletions