[clang][bytecode] Don't crash on erroneous switch conditions (llvm#147533)

Not attaching a test since I've only seen this when compiling a large
c++26 test case as c++17.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -5629,6 +5629,9 @@ bool Compiler<Emitter>::visitContinueStmt(const ContinueStmt *S) {
 template <class Emitter>
 bool Compiler<Emitter>::visitSwitchStmt(const SwitchStmt *S) {
   const Expr *Cond = S->getCond();
+  if (Cond->containsErrors())
+    return false;
+
   PrimType CondT = this->classifyPrim(Cond->getType());
   LocalScope<Emitter> LS(this);