Fix #14701: avoid REPL crash when input is of the form val _ = ???

The REPL should not crash when the right hand side of `val _ =`
throws a non-fatal error that is a subclass of java.lang.Error.

compiler/src/dotty/tools/repl/Rendering.scala

@@ -142,11 +142,15 @@ private[repl] class Rendering(parentClassLoader: Option[ClassLoader] = None) {
 
   /** Force module initialization in the absence of members. */
   def forceModule(sym: Symbol)(using Context): Seq[Diagnostic] =
+    import scala.util.control.NonFatal
     def load() =
       val objectName = sym.fullName.encode.toString
       Class.forName(objectName, true, classLoader())
       Nil
-    try load() catch case e: ExceptionInInitializerError => List(renderError(e, sym.denot))
+    try load()
+    catch
+      case e: ExceptionInInitializerError => List(renderError(e, sym.denot))
+      case NonFatal(e) => List(renderError(InvocationTargetException(e), sym.denot))
 
   /** Render the stack trace of the underlying exception. */
   def renderError(ite: InvocationTargetException | ExceptionInInitializerError, d: Denotation)(using Context): Diagnostic =

compiler/test/dotty/tools/repl/ReplCompilerTests.scala

@@ -334,6 +334,19 @@ class ReplCompilerTests extends ReplTest:
     assertEquals("scala.MatchError: hi (of class java.lang.String)", all.head)
   }
 
+  @Test def i14701 = initially {
+    val state = run("val _ = ???")
+    val all = lines()
+    assertEquals(3, all.length)
+    assertEquals("scala.NotImplementedError: an implementation is missing", all.head)
+    state
+  } andThen {
+    run("val _ = assert(false)")
+    val all = lines()
+    assertEquals(3, all.length)
+    assertEquals("java.lang.AssertionError: assertion failed", all.head)
+  }
+
   @Test def i14491 =
     initially {
       run("import language.experimental.fewerBraces")