Issue 25219. Fix for RangeError during converting empty lines in /// comments.

pkg/analysis_server/test/services/correction/assist_test.dart

 // Copyright (c) 2014, 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.
 
 library test.services.correction.assist;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/edit/assist/assist_core.dart';
 import 'package:analysis_server/plugin/protocol/protocol.dart';
@@ skipping 857 matching lines @@
 
   test_convertDocumentationIntoBlock_BAD_notDocumentation() async {
     resolveTestUnit('''
 // AAAA
 class A {}
 ''');
     await assertNoAssistAt(
         'AAA', DartAssistKind.CONVERT_DOCUMENTATION_INTO_BLOCK);
   }
 
+  test_convertDocumentationIntoBlock_OK_noSpaceBeforeText() async {
+    resolveTestUnit('''
+class A {
+  /// AAAAA
+  ///BBBBB
+  ///
+  /// CCCCC
+  mmm() {}
+}
+''');
+    await assertHasAssistAt(
+        'AAAAA',
+        DartAssistKind.CONVERT_DOCUMENTATION_INTO_BLOCK,
+        '''
+class A {
+  /**
+   * AAAAA
+   *BBBBB
+   *
+   * CCCCC
+   */
+  mmm() {}
+}
+''');
+  }
+
   test_convertDocumentationIntoBlock_OK_onReference() async {
     resolveTestUnit('''
 /// AAAAAAA [int] AAAAAAA
 class A {}
 ''');
     await assertHasAssistAt(
         'nt]',
         DartAssistKind.CONVERT_DOCUMENTATION_INTO_BLOCK,
         '''
 /**
@@ skipping 3032 matching lines @@
       positions.add(new Position(testFile, offset));
     }
     return positions;
   }
 
   void _setStartEndSelection() {
     offset = findOffset('// start\n') + '// start\n'.length;
     length = findOffset('// end') - offset;
   }
 }