patch 8.2.1468: Vim9: invalid error for missing white space

Problem:    Vim9: invalid error for missing white space.
Solution:   Don't skip over white space after index. (closes #6718)

src/eval.c

@@ -3624,7 +3624,7 @@ eval_index(
 		clear_tv(&var2);
 	    return FAIL;
 	}
-	*arg = skipwhite(*arg + 1);	// skip the ']'
+	*arg = *arg + 1;	// skip over the ']'
     }
 
     if (evaluate)

src/testdir/test_vim9_expr.vim

@@ -827,6 +827,13 @@ def Test_expr4_vim9script()
     echo len('xxx') == 3
   END
   CheckScriptSuccess(lines)
+
+  lines =<< trim END
+    vim9script
+    let line = 'abc'
+    echo line[1] =~ '\w'
+  END
+  CheckScriptSuccess(lines)
 enddef
 
 func Test_expr4_fails()

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1468,
 /**/
     1467,
 /**/