patch 8.1.0564: setting v:errors to wrong type still possible

Problem:    Setting v:errors to wrong type still possible.
Solution:   Return after giving an error message. (Christian Brabandt)

src/eval.c

@@ -7568,7 +7568,10 @@ set_var(
 		return;
 	    }
 	    else if (v->di_tv.v_type != tv->v_type)
+	    {
 		EMSG2(_("E963: setting %s to value with wrong type"), name);
+		return;
+	    }
 	}
 
 	clear_tv(&v->di_tv);

src/testdir/test_eval_stuff.vim

@@ -53,3 +53,13 @@ func Test_line_continuation()
 	"\ and some more
   call assert_equal([5, 6], array)
 endfunc
+
+func Test_E963()
+  " These commands used to cause an internal error prior to vim 8.1.0563
+  let v_e = v:errors
+  let v_o = v:oldfiles
+  call assert_fails("let v:errors=''", 'E963:')
+  call assert_equal(v_e, v:errors)
+  call assert_fails("let v:oldfiles=''", 'E963:')
+  call assert_equal(v_o, v:oldfiles)
+endfunc

src/version.c

@@ -792,6 +792,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    564,
 /**/
     563,
 /**/