try to fix memory leak in QuadCommand

[summerinsects]

#18140

I'm not sure whether it will break compatibility

[minggo]

why it has memory leak?

[summerinsects]

For static GLushort* QuadCommand::__indices, which was newed in method QuadCommand::reIndex, nowhere deleted it

[minggo]

When resizing index, old indices are pushed into _ownedIndices, which is freed in destructor.

[summerinsects]

but the the last time allocation was not freed.
I debug it on vs with crt library functions _CrtDumpMemoryLeaks and _CrtSetBreakAlloc, and it breaks here

[minggo]

We uses it as a cache, don't freed the last one or we will malloc/free memories all the time. vs debugger doesn't treat global memory well.