Don't NPE on op ._ when translating tree to IR (#8381)

Encountered a random NPE when playing with bookclubs. Test case demonstrating the problem is attached.

Threw in a bunch of minor tweaks to logs to make life of the person debugging code more pleasant.

engine/language-server/src/main/resources/application.conf

@@ -40,6 +40,7 @@ logging-service {
     org.enso.languageserver.protocol.json.JsonConnectionController = debug
     org.enso.jsonrpc.JsonRpcServer = debug
     org.enso.languageserver.runtime.RuntimeConnector = debug
+    org.enso.interpreter.runtime.HostClassLoader = error
   }
   appenders = [
     {

engine/runtime-compiler/src/main/java/org/enso/compiler/context/CompilerContext.java

@@ -43,6 +43,8 @@ public interface CompilerContext extends CompilerStub {
 
   void log(Level level, String msg, Object... args);
 
+  void log(Level level, String msg, Throwable ex);
+
   void logSerializationManager(Level level, String msg, Object... args);
 
   void notifySerializeModule(QualifiedName moduleName);

engine/runtime-instrument-common/src/main/scala/org/enso/interpreter/instrument/command/AttachVisualizationCmd.scala

@@ -26,7 +26,7 @@ class AttachVisualizationCmd(
   ): Future[Unit] = {
     ctx.executionService.getLogger.log(
       Level.FINE,
-      "Attach visualization cmd for request id [{}] and visualization id [{}]",
+      "Attach visualization cmd for request id [{0}] and visualization id [{1}]",
       Array(maybeRequestId, request.visualizationId)
     )
     ctx.endpoint.sendToClient(

engine/runtime-instrument-common/src/main/scala/org/enso/interpreter/instrument/job/UpsertVisualizationJob.scala

@@ -139,7 +139,7 @@ class UpsertVisualizationJob(
   )(implicit ctx: RuntimeContext): Unit = {
     ctx.executionService.getLogger.log(
       Level.SEVERE,
-      "Visualization for expression {0} failed: {1} (evaluation result: {2}",
+      "Visualization for expression {0} failed: {1} (evaluation result: {2})",
       Array(expressionId, message, executionResult)
     )
     ctx.endpoint.sendToClient(

engine/runtime-parser/src/main/java/org/enso/compiler/core/TreeToIr.java

@@ -1438,7 +1438,11 @@ final class TreeToIr {
       } else {
         throw translateEntity(app, Syntax.UnexpectedExpression$.MODULE$);
       }
+      if (app.getLhs() != null) {
         list = app.getLhs();
+      } else {
+        throw translateEntity(app, Syntax.UnexpectedExpression$.MODULE$);
+      }
     }
     segments.add(list);
     java.util.Collections.reverse(segments);

engine/runtime/src/main/java/org/enso/interpreter/runtime/TruffleCompilerContext.java

@@ -93,6 +93,11 @@ final class TruffleCompilerContext implements CompilerContext {
     loggerCompiler.log(level, msg, args);
   }
 
+  @Override
+  public void log(Level level, String msg, Throwable ex) {
+    loggerCompiler.log(level, msg, ex);
+  }
+
   @Override
   public void logSerializationManager(Level level, String msg, Object... args) {
     loggerSerializationManager.log(level, msg, args);

engine/runtime/src/test/java/org/enso/compiler/ErrorCompilerTest.java

@@ -30,6 +30,16 @@ public class ErrorCompilerTest extends CompilerTest {
     assertSingleSyntaxError(ir, Syntax.InvalidUnderscore$.MODULE$, "Invalid use of _", 14, 15);
   }
 
+  @Test
+  public void spaceDotUnderscore() throws Exception {
+    var ir = parse("""
+    run op =
+      op ._
+    """);
+
+    assertSingleSyntaxError(ir, Syntax.UnexpectedExpression$.MODULE$, "Unexpected expression", 14, 16);
+  }
+
   @Test
   public void unaryMinus() throws Exception {
     var ir = parse("""