fix: prevent infinite loop when processing TS files with no subtitles

[DhanushVarma-2]

Problem:
When processing TS files containing no subtitles, ccextractor enters an infinite loop and floods the terminal with binary output instead of exiting gracefully (Issue #1754).

Root Cause:
The ts_readstream function in ts_functions.c had a do-while (!gotpes) loop that would run indefinitely when no subtitle streams were detected, because gotpes never became true in files without subtitles.

Solution:

• Added a packet counter to track how many packets have been processed
• Set a reasonable limit (50,000 packets) after which processing stops if no subtitles are found
• Added subtitle_found flag that gets set when actual caption data is processed
• Clean exit with debug message when no subtitles are detected

Changes Made:

• src/lib_ccx/ts_functions.c: Added termination condition in ts_readstream function

Testing

• ✅ Code compiles successfully without errors
• ✅ Basic functionality verified (version, help commands work)
• ✅ Error handling works properly
• ✅ The fix maintains backward compatibility for files with subtitles

Fixes #1754

[ccextractor-bot]

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 42d7509...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	7/7
DVD	3/3
DVR-MS	2/2
General	27/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	86/86
Teletext	21/21
WTV	13/13
XDS	34/34

Congratulations: Merging this PR would fix the following tests:

• ccextractor --hardsubx 1a0302f7fd..., Last passed: Never

All tests passing on the master branch were passed completely.

Check the result page for more info.