[F3D] Fixed two issues with ex3 cellshading (#380)

Check for f3dex3 GBI before for writing cel levels, and remove the icon="Error" keyword argument that was causing the exception raise to fail

fast64_internal/f3d/f3d_writer.py

@@ -999,7 +999,7 @@ def processGeometry(self):
         triCmds = createTriangleCommands(
             self.vertexBufferTriangles, self.vertBuffer, not self.triConverterInfo.f3d.F3D_OLD_GBI
         )
-        if not self.material.f3d_mat.use_cel_shading:
+        if not self.triConverterInfo.f3d.F3DEX_GBI_3 or not self.material.f3d_mat.use_cel_shading:
             self.triList.commands.extend(triCmds)
         else:
             if len(triCmds) <= 2:
@@ -1021,8 +1021,7 @@ def writeCelLevels(self, celTriList: Optional[GfxList] = None, triCmds: Optional
         # first before switching to decal.
         if f3dMat.rdp_settings.zmode != "ZMODE_OPA":
             raise PluginError(
-                f"Material {self.material.name} with cel shading: zmode in blender / rendermode must be opaque.",
-                icon="ERROR",
+                f"Material {self.material.name} with cel shading: zmode in blender / rendermode must be opaque."
             )
         wroteLighter = wroteDarker = usesDecal = False
         if len(cel.levels) == 0: