patch 9.1.1087: Vim9: import with extends may crash

Problem:  Vim9: import with extends may crash
Solution: check otv for being NULL before trying to access it
          (Hirohito Higashi)

closes: #16601

Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_vim9_import.vim b/src/testdir/test_vim9_import.vim
index ff81f4a..c8dfa1e 100644
--- a/src/testdir/test_vim9_import.vim
+++ b/src/testdir/test_vim9_import.vim
@@ -3420,4 +3420,42 @@
   v9.CheckScriptSuccess(lines)
 enddef
 
+" Test for don't crash when using a combination of import and class extends
+def Test_vim9_import_and_class_extends()
+  var lines =<< trim END
+    vim9script
+    import './cccc.vim'
+    export class Property extends cccc.Run
+      public var value: string
+      def new(this.value)
+      cccc.Run.value2 = this.value
+    enddef
+    endclass
+  END
+  writefile(lines, './aaaa.vim', 'D')
+
+  lines =<< trim END
+    vim9script
+    export class Run
+      public var value2: string
+      def new(this.value)
+      enddef
+    endclass
+  END
+  writefile(lines, './cccc.vim', 'D')
+
+  lines =<< trim END
+    vim9script
+    import './aaaa.vim'
+    class View
+      var content = aaaa.Property.new('')
+    endclass
+
+    var myView = View.new('This should be ok')
+    assert_equal('This should be ok', myView.content.value)
+  END
+  # TODO: The root cause will be identified later.
+  v9.CheckScriptFailure(lines, 'E1099: Unknown error while executing new', 7)
+enddef
+
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker
diff --git a/src/version.c b/src/version.c
index b8f783e..01ce873 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1087,
+/**/
     1086,
 /**/
     1085,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index c7f0e67..5022000 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -2461,8 +2461,14 @@
 		otv = class->class_members_tv;
 	    }
 
-	    clear_tv(&otv[lidx]);
-	    otv[lidx] = *tv;
+	    if (otv != NULL)
+	    {
+		clear_tv(&otv[lidx]);
+		otv[lidx] = *tv;
+	    }
+	    else
+		status = FAIL;
+
 	}
 	else
 	{