draw: Don't assert if indices point outside vertex buffer.

draw: Don't assert if indices point outside vertex buffer.

This is valid input, and asserting here does causes the test suites that
verify this to crash.

Also, the assert was wrongly accepting the case

  max_index == vert_info->count

which, IIUC, is the first vertex outside the buffer. Assuming the
vert_info->count is precise (which often is not the case).