Fixed RasPi builds of unit tests.

On RasPi with gcc 4.8.2, the asserts wouldn't compile when tests were enabled.
Enforced the assumption that ASSERT code is generated only in Debug builds.

src/Entities/EntityEffect.cpp

@@ -217,7 +217,9 @@ cEntityEffect * cEntityEffect::CreateEntityEffect(cEntityEffect::eType a_EffectT
 	}
 
 	ASSERT(!"Unhandled entity effect type!");
-	return nullptr;
+	#ifndef __clang__
+		return nullptr;
+	#endif
 }