Fixes #324, texture slot raises exception when image is None, and add…

…s new unit test

io_xplane2blender/xplane_types/xplane_material.py

@@ -174,30 +174,37 @@ def collect(self):
         self.attributes.order()
 
     def _detectTextures(self, mat):
+        '''
+        Detects the texture by using Blender's texture slot properties:
+        Diffuse->Color, Shading->Emit, Geometry->Normal, and Specular-> Intensity
+        '''
         for i in range(0, len(mat.texture_slots)):
             slot = mat.texture_slots[i]
 
             if slot and slot.use and slot.texture.type == 'IMAGE':
-                #Props->Texture->Influence->Diffuse->[X] Color
-                if slot.use_map_color_diffuse and self.texture == None:
-                    self.texture = slot.texture.image.filepath
-                #Props->Texture->Influence->Shading->[X] Emit
-                elif slot.use_map_emit and self.textureLit == None:
-                    self.textureLit = slot.texture.image.filepath
-                #Props->Texture->Influence->Geometry->[X] Normal
-                elif slot.use_map_normal and self.textureNormal == None:
-                    self.textureNormal = slot.texture.image.filepath
-                #Props->Texture->Influence->Specular->[X] Intensity
-                elif slot.use_map_specular and self.textureSpecular == None:
-                    self.textureSpecular = slot.texture.image.filepath
+                if slot.texture.image is not None:
+                    #Props->Texture->Influence->Diffuse->[X] Color
+                    if slot.use_map_color_diffuse and self.texture == None:
+                        self.texture = slot.texture.image.filepath
+                    #Props->Texture->Influence->Shading->[X] Emit
+                    elif slot.use_map_emit and self.textureLit == None:
+                        self.textureLit = slot.texture.image.filepath
+                    #Props->Texture->Influence->Geometry->[X] Normal
+                    elif slot.use_map_normal and self.textureNormal == None:
+                        self.textureNormal = slot.texture.image.filepath
+                    #Props->Texture->Influence->Specular->[X] Intensity
+                    elif slot.use_map_specular and self.textureSpecular == None:
+                        self.textureSpecular = slot.texture.image.filepath
+                else:
+                    logger.error("Texture '{0}' has no image".format(slot.texture.name))
+                    return
 
         # panel materials have only a color texture
         if self.options.panel:
             self.textureLit = None
             self.textureNormal = None
             self.textureSpecular = None
 
-
     def collectCustomAttributes(self, mat):
         xplaneFile = self.xplaneObject.xplaneBone.xplaneFile
         commands =  xplaneFile.commands

tests/materials/objects/texture_slot_has_no_image.test.py

@@ -0,0 +1,16 @@
+import bpy
+import os
+import inspect
+import sys
+
+from io_xplane2blender.tests import *
+from io_xplane2blender import xplane_config
+
+__dirname__ = os.path.dirname(__file__)
+
+class TestTextureSlotHasNoImage(XPlaneTestCase):
+    def test_texture_slot_has_no_image(self):
+        out  = self.exportLayer(0)
+        self.assertLoggerErrors(1)
+
+runTestCases([TestTextureSlotHasNoImage])