patch 9.0.1091: assignment to non-existing member causes a crash

Problem:    Assignment to non-existing member causes a crash. (Yegappan
            Lakshmanan)
Solution:   Give an error message and bail out when a member cannot be found.
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index f45e3fa..88128e7 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -111,6 +111,17 @@
   lines =<< trim END
       vim9script
       class Something
+        def new()
+          this.state = 0
+        enddef
+      endclass
+      var obj = Something.new()
+  END
+  v9.CheckScriptFailure(lines, 'E1089:')
+
+  lines =<< trim END
+      vim9script
+      class Something
         this.count : number
       endclass
   END
@@ -330,7 +341,9 @@
       assert_equal(0, TextPos.counter)
       TextPos.AddToCounter(3)
       assert_equal(3, TextPos.counter)
+      assert_fails('echo TextPos.noSuchMember', 'E1338:')
 
+      assert_fails('TextPos.noSuchMember = 2', 'E1337:')
       assert_fails('TextPos.counter += 5', 'E1335')
   END
   v9.CheckScriptSuccess(lines)