Add missing suspendability check

Author: nicolasstucki

compiler/src/dotty/tools/dotc/quoted/Interpreter.scala

@@ -346,7 +346,8 @@ object Interpreter:
 
   object MissingClassDefinedInCurrentRun {
     def unapply(targetException: Throwable)(using Context): Option[Symbol] = {
-      targetException match
+      if !ctx.compilationUnit.isSuspendable then None
+      else targetException match
         case _: NoClassDefFoundError | _: ClassNotFoundException =>
           val className = targetException.getMessage
           if className eq null then None