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>

src/testdir/test_vim9_import.vim

@@ -3420,4 +3420,42 @@ def Test_imported_class_as_def_func_rettype()
   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

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1087,
 /**/
     1086,
 /**/

src/vim9execute.c

@@ -2461,8 +2461,14 @@ execute_storeindex(isn_T *iptr, ectx_T *ectx)
 		otv = class->class_members_tv;
 	    }
 
-	    clear_tv(&otv[lidx]);
+	    if (otv != NULL)
-	    otv[lidx] = *tv;
+	    {
+		clear_tv(&otv[lidx]);
+		otv[lidx] = *tv;
+	    }
+	    else
+		status = FAIL;
+
 	}
 	else
 	{