Internals: Add assertions. No functional change intended.

src/V3Descope.cpp

@@ -104,6 +104,7 @@ private:
         //
         // V3Combine wouldn't likely be able to combine top-level
         // routines anyway, so there's no harm in keeping these static.
+        UASSERT_OBJ(m_modp, scopep, "Scope not under module");
         if (m_modp->isTop()) relativeRefOk = false;
         //
         // Use absolute refs if this scope is the only instance of the module.