Some binary files are shown in source viewer (BB-1763)

Binary files (or some of them?) are shown in the source view embedded in HTML. This is not really useful and makes some browers crash.

Example:
go to https://bitbucket.org/skoe/easyflash/src/6103b096b9a3/EasySDK/\\
then click directly on:
EasySDK.pdf

My expection would be something like "Binary file detected, preview disabled."