[BUGFIX] Also check if cache files are not empty

If the temp_CACHED* files exist, but they are empty a lot of functions
produce incorrect result due to missing TCA data. Checking the fileSize
prevents the use of empty cache files.

Change-Id: I855034048eca142153badd2567fb2bf6dfbc2629
Resolves: #29075
Branches: 4.6, 4.5, 4.4, 4.3
Reviewed-on: http://review.typo3.org/4420
Reviewed-by: Björn Pedersen
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn