Past releases, when rendering an invalid primary texture, would
Int3() and then reset the texture to zero. Commit d767f7c changed the
logic to return without resetting the texture, since the reset seemed to
be unnecessary. Unfortunately, it is necessary. Some levels, including
those shipped with the retail game data, specify bogus primary textures
on some surfaces. After d767f7c, rendering a surface with an invalid
primary texture causes the surface to be invisible, even if it has a
valid secondary texture.
Remove the return statement added in d767f7c. Extend
validate_segment_side to validate the primary texture on the tested
side. When an invalid texture is found, reset it and log a diagnostic.
For built-in levels, log at level CON_VERBOSE since players cannot
readily fix the level. For external levels, log at level CON_URGENT so
that level authors know to fix their level before releasing it.
Fixes: d767f7cd5e ("Pass vcsegptridx to render_face")
