Debug|World: Avoid crash when analyzing alpha of a missing sprite tex…

…ture

IssueID #1964

doomsday/client/src/world/p_mobj.cpp

@@ -568,19 +568,22 @@ float Mobj_ShadowStrength(mobj_t *mo)
 
                 TextureVariant const *texture = matAnimator.texUnit(MaterialAnimator::TU_LAYER0).texture;
                 DENG2_ASSERT(texture);
-                auto const *aa = (averagealpha_analysis_t const *)texture->base().analysisDataPointer(Texture::AverageAlphaAnalysis);
-                DENG2_ASSERT(aa);
+                if(texture)
+                {
+                    auto const *aa = (averagealpha_analysis_t const *)texture->base().analysisDataPointer(Texture::AverageAlphaAnalysis);
+                    DENG2_ASSERT(aa);
 
-                // We use an average which factors in the coverage ratio
-                // of alpha:non-alpha pixels.
-                /// @todo Constant weights could stand some tweaking...
-                float weightedSpriteAlpha = aa->alpha * (0.4f + (1 - aa->coverage) * 0.6f);
+                    // We use an average which factors in the coverage ratio
+                    // of alpha:non-alpha pixels.
+                    /// @todo Constant weights could stand some tweaking...
+                    float weightedSpriteAlpha = aa->alpha * (0.4f + (1 - aa->coverage) * 0.6f);
 
-                // Almost entirely translucent sprite? => no shadow.
-                if(weightedSpriteAlpha < minSpriteAlphaLimit) return 0;
+                    // Almost entirely translucent sprite? => no shadow.
+                    if(weightedSpriteAlpha < minSpriteAlphaLimit) return 0;
 
-                // Apply this factor.
-                strength *= de::min(1.f, .2f + weightedSpriteAlpha);
+                    // Apply this factor.
+                    strength *= de::min(1.f, .2f + weightedSpriteAlpha);
+                }
             }
         }
     }