Lightmap Mod: Don't expose tracebacks to the user

Rather, inform the user in a standardized way when nothing was baked.
Beats the heck out of seeing a random traceback!

korman/exporter/etlight.py

@@ -69,11 +69,12 @@ class LightBaker:
         with GoodNeighbor() as toggle:
             try:
                 # reduce the amount of indentation
-                self._bake_static_lighting(bake, toggle)
+                result = self._bake_static_lighting(bake, toggle)
             finally:
                 # this stuff has been observed to be problematic with GoodNeighbor
                 self._pop_lightgroups()
                 self._restore_uvtexs()
+            return result
 
     def _bake_static_lighting(self, bake, toggle):
         # Step 0.9: Make all layers visible.
@@ -112,6 +113,9 @@ class LightBaker:
             else:
                 raise RuntimeError(key[0])
 
+        # Return how many thingos we baked
+        return sum(map(sum, bake.values()))
+
     def _generate_lightgroup(self, mesh, user_lg=None):
         """Makes a new light group for the baking process that excludes all Plasma RT lamps"""
 

korman/operators/op_lightmap.py

@@ -42,7 +42,9 @@ class LightmapAutobakePreviewOperator(_LightingOperator, bpy.types.Operator):
             toggle.track(context.scene, "layers", tuple(context.scene.layers))
 
             bake = LightBaker()
-            bake.bake_static_lighting([context.active_object,])
+            if not bake.bake_static_lighting([context.active_object,]):
+                self.report({"INFO"}, "No valid lights found to bake.")
+                return {"FINISHED"}
 
         tex = bpy.data.textures.get("LIGHTMAPGEN_PREVIEW")
         if tex is None:

korman/ui/modifiers/render.py

@@ -59,7 +59,7 @@ def lightmap(modifier, layout, context):
     # the backing image name to see if it's for this lightmap. If so, you have a preview. If not,
     # well... It was nice knowing you!
     tex = bpy.data.textures.get("LIGHTMAPGEN_PREVIEW")
-    if tex is not None:
+    if tex is not None and tex.image is not None:
         im_name = "{}_LIGHTMAPGEN.png".format(context.active_object.name)
         if tex.image.name == im_name:
             layout.template_preview(tex, show_buttons=False)