Fix bugs in the log viewer

pkg/analysis_server/tool/instrumentation/page/log_page.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:math' as math;
 
 import '../log/log.dart';
 import '../server.dart';
 import 'page_writer.dart';
 
@@ skipping 207 matching lines @@
       sink.write(group.id);
       sink.write('"');
       if (group == selectedGroup) {
         sink.write(' selected');
       }
       sink.write('>');
       sink.write(group.name);
       sink.writeln('</option>');
     }
     sink.writeln('</select>');
-    sink.writeln('Events $pageStart - ${pageEnd - 1} of ${length - 1}');
+    if (length == 0) {
+      sink.writeln('No matching events');
+    } else {
+      sink.writeln('Events $pageStart - ${pageEnd - 1} of $length');
+    }
     sink.writeln('</div>');
 
     sink.writeln('<div style="float: right">');
     if (pageStart == 0) {
       sink.writeln('<button type="button" disabled><b>&lt;</b></button>');
     } else {
       sink.write('<button type="button">');
       sink.write(
           '<a href="${WebServer.logPath}?group=${selectedGroup.id}&start=${pageStart - pageLength}">');
       sink.write('<b>&lt;</b>');
@@ skipping 34 matching lines @@
   void _writeRightColumn(StringSink sink) {
     //
     // Write the header of the column.
     //
     sink.writeln('<div class="columnHeader">');
     sink.writeln('<p><b>Entry Details</b></p>');
     sink.writeln('</div>');
     sink.writeln('<div id="details"></div>');
   }
 }