Atomics: fix invalid index; print error

test/built-ins/Atomics/wake/null-bufferdata-throws.js

@@ -29,7 +29,7 @@ const poisoned = {
 try {
   $DETACHBUFFER(i32a.buffer); // Detaching a non-shared ArrayBuffer sets the [[ArrayBufferData]] value to null
 } catch (error) {
-  $ERROR(`An unexpected error occurred when detaching ArrayBuffer: ${error.message}`);
+  $ERROR(`An unexpected error occurred when detaching ArrayBuffer: ${error}`);
 }
 
 assert.throws(TypeError, function() {

test/built-ins/Atomics/wake/out-of-range-index-throws.js

@@ -30,8 +30,8 @@ assert.throws(RangeError, function() {
   Atomics.wake(i32a, Infinity, poisoned);
 }, '`Atomics.wake(i32a, Infinity, poisoned)` throws RangeError');
 assert.throws(RangeError, function() {
-  Atomics.wake(i32a, 2, poisoned);
-}, '`Atomics.wake(i32a, 2, poisoned)` throws RangeError');
+  Atomics.wake(i32a, 4, poisoned);
+}, '`Atomics.wake(i32a, 4, poisoned)` throws RangeError');
 assert.throws(RangeError, function() {
   Atomics.wake(i32a, 200, poisoned);
 }, '`Atomics.wake(i32a, 200, poisoned)` throws RangeError');