SILVerifier: Fix the opened c-o-w existential check for debug_value_addr instruction

Author: aschwaighofer

lib/SIL/SILVerifier.cpp

@@ -2255,6 +2255,9 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
               CastConsumptionKind::CopyOnSuccess)
             return true;
           break;
+        case ValueKind::DebugValueAddrInst:
+          // Harmless use.
+          break;
         default:
           assert(false && "Unhandled unexpected instruction");
           break;