Uploader: make sure CRCFromQBArray is safe

Previously if the size to pad was less than the file size
it would create an enormous array and crash.
Uploader: do not show CRC for invalid files

If the loaded file is longer than the available flash then
calculating the CRC is meaningless as it would not go into
the chip.
Merge pull request #1393 from peabody124/uploader_crash_fix

Uploader: calculate CRC based on current file size