NFC: add a few module asserts

Author: kavon

lib/AST/ASTPrinter.cpp

@@ -1093,6 +1093,7 @@ class PrintAST : public ASTVisitor<PrintAST> {
     Type OldType = CurrentType;
     if (CurrentType && (Old != nullptr || Options.PrintAsMember)) {
       if (auto *NTD = dyn_cast<NominalTypeDecl>(D)) {
+        assert(Options.CurrentModule);
         auto Subs = CurrentType->getContextSubstitutionMap(
           Options.CurrentModule, NTD->getDeclContext());
         setCurrentType(NTD->getDeclaredInterfaceType().subst(Subs));

lib/AST/TypeSubstitution.cpp

@@ -211,6 +211,7 @@ operator()(CanType dependentType, Type conformingReplacementType,
   if (conformingReplacementType->isTypeParameter())
     return ProtocolConformanceRef(conformedProtocol);
 
+  assert(M && "null module in conformance lookup");
   return M->lookupConformance(conformingReplacementType,
                               conformedProtocol,
                               /*allowMissing=*/true);