patch 8.2.3847: illegal memory access when using a lambda with an error

Problem:    Illegal memory access when using a lambda with an error.
Solution:   Avoid skipping over the NUL after a string.

src/eval.c

@@ -3871,12 +3871,15 @@ eval_lambda(
 	++*arg;
 	ret = eval1(arg, rettv, evalarg);
 	*arg = skipwhite_and_linebreak(*arg, evalarg);
-	if (**arg != ')')
+	if (**arg == ')')
+	{
+	    ++*arg;
+	}
+	else
 	{
 	    emsg(_(e_missing_closing_paren));
 	    ret = FAIL;
 	}
-	++*arg;
     }
     if (ret != OK)
 	return FAIL;

src/testdir/test_lambda.vim

@@ -64,6 +64,8 @@ function Test_lambda_fails()
   call assert_fails('echo {a, a -> a + a}(1, 2)', 'E853:')
   call assert_fails('echo {a, b -> a + b)}(1, 2)', 'E451:')
   echo assert_fails('echo 10->{a -> a + 2}', 'E107:')
+
+  call assert_fails('eval 0->(', "E110: Missing ')'")
 endfunc
 
 func Test_not_lamda()

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3847,
 /**/
     3846,
 /**/