Fix sending empty yarp::sig::Vector when building in Debug

[traversaro]

Before this PR, sending an empty yarp::sig::Vector on port in Debug mode resulted in a crash of the application attempting to do that:

(yarpdev) traversaro@IITBMP014LW012:~/pixiws/yarpdev/yarp/build$ ctest -R VectorOf -VV
UpdateCTestConfiguration  from :/home/traversaro/pixiws/yarpdev/yarp/build/DartConfiguration.tcl
UpdateCTestConfiguration  from :/home/traversaro/pixiws/yarpdev/yarp/build/DartConfiguration.tcl
Test project /home/traversaro/pixiws/yarpdev/yarp/build
Constructing a list of tests
Done constructing a list of tests
Updating test list for fixtures
Added 0 tests to meet fixture requirements
Checking test dependency graph...
Checking test dependency graph end
test 73
    Start 73: sig::VectorOfTest

73: Test command: /home/traversaro/pixiws/yarpdev/yarp/build/bin/harness_sig "sig::VectorOfTest" "-s" "--colour-mode default"
73: Working Directory: /home/traversaro/pixiws/yarpdev/yarp/build/src/libYARP_sig/tests
73: Test timeout computed to be: 120
73: Filters: "sig::VectorOfTest"
73: Randomness seeded to: 3429436721
73: [INFO] |yarp.os.Port|/harness_sig/vtest/o| Port /harness_sig/vtest/o active at tcp://localhost:10002/
73: [INFO] |yarp.os.Port|/harness_sig/vtest/i| Port /harness_sig/vtest/i active at tcp://localhost:10003/
73: [INFO] |yarp.os.impl.PortCoreInputUnit|/harness_sig/vtest/i| Receiving input from /harness_sig/vtest/o to /harness_sig/vtest/i using tcp
73: [INFO] |yarp.os.impl.PortCoreOutputUnit|/harness_sig/vtest/o| Sending output from /harness_sig/vtest/o to /harness_sig/vtest/i using tcp
73:
73: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
73: harness_sig is a Catch2 v3.4.0 host application.
73: Run with -? for options
73:
73: -------------------------------------------------------------------------------
73: sig::VectorOfTest
73:   Check send and receive integers
73: -------------------------------------------------------------------------------
73: /home/traversaro/pixiws/yarpdev/yarp/src/libYARP_sig/tests/VectorOfTest.cpp:31
73: ...............................................................................
73:
73: /home/traversaro/pixiws/yarpdev/yarp/src/libYARP_sig/tests/VectorOfTest.cpp:74: PASSED:
73:   CHECK( success )
73: with expansion:
73:   true
73: with message:
73:   check VectorO<int> send receive
73:
73: [INFO] |yarp.os.impl.PortCoreInputUnit|/harness_sig/vtest/i| Removing input from /harness_sig/vtest/o to /harness_sig/vtest/i
73: [INFO] |yarp.os.impl.PortCoreOutputUnit|/harness_sig/vtest/o| Removing output from /harness_sig/vtest/o to /harness_sig/vtest/i
73: [INFO] |yarp.os.Port|/harness_sig/vtest/empty_vector/o| Port /harness_sig/vtest/empty_vector/o active at tcp://localhost:10004/
73: [INFO] |yarp.os.Port|/harness_sig/vtest/empty_vector/i| Port /harness_sig/vtest/empty_vector/i active at tcp://localhost:10005/
73: [INFO] |yarp.os.impl.PortCoreOutputUnit|/harness_sig/vtest/empty_vector/o| Sending output from /harness_sig/vtest/empty_vector/o to /harness_sig/vtest/empty_vector/i using tcp
73: [INFO] |yarp.os.impl.PortCoreInputUnit|/harness_sig/vtest/empty_vector/i| Receiving input from /harness_sig/vtest/empty_vector/o to /harness_sig/vtest/empty_vector/i using tcp
73: [FATAL] |yarp.sig.Vector| Assertion failure at /home/traversaro/pixiws/yarpdev/yarp/src/libYARP_sig/src/yarp/sig/Vector.cpp:89 (ptr != nullptr)
73: Trace requested at /home/traversaro/pixiws/yarpdev/yarp/src/libYARP_sig/src/yarp/sig/Vector.cpp:89 by code called from:
73: /home/traversaro/pixiws/yarpdev/yarp/build/lib/libYARP_os.so.3(_Z16yarp_print_traceP8_IO_FILEPKcj+0x36) [0x7f210827cd66]
73: /home/traversaro/pixiws/yarpdev/yarp/build/lib/libYARP_os.so.3(_ZNK4yarp2os3Log5fatalEPKcz+0xbe) [0x7f210827ce7e]
73: /home/traversaro/pixiws/yarpdev/yarp/build/lib/libYARP_sig.so.3(_ZNK4yarp3sig10VectorBase5writeERNS_2os16ConnectionWriterE+0x10a) [0x7f210840888a]
73: /home/traversaro/pixiws/yarpdev/yarp/build/lib/libYARP_os.so.3(+0x158fb3) [0x7f2108357fb3]
73: /home/traversaro/pixiws/yarpdev/yarp/build/lib/libYARP_os.so.3(+0x1599c6) [0x7f21083589c6]
73: /home/traversaro/pixiws/yarpdev/yarp/build/lib/libYARP_os.so.3(+0x16c8a5) [0x7f210836b8a5]
73: /home/traversaro/pixiws/yarpdev/.pixi/envs/default/lib/libstdc++.so.6(+0xd3b55) [0x7f21080edb55]
73: /lib/x86_64-linux-gnu/libc.so.6(+0x9ca94) [0x7f2107d7da94]
73: /lib/x86_64-linux-gnu/libc.so.6(+0x129c3c) [0x7f2107e0ac3c]
1/1 Test #73: sig::VectorOfTest ................***Failed    0.02 sec

This PR fixes this problem, and add a test ensuring that empty yarp::sig::Vector can be successfully be transmitted on the YARP network.

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would update the release notes by adding a file in doc/release/<target_branch>, based on your changes.

[traversaro]

fyi @LoreMoretti

[sonarcloud]

Quality Gate failed

Failed conditions
60.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud

[traversaro]

Quality Gate failed

Failed conditions 61.2% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud

I am not sure about this, it is complaining that the test code is not covered by tests?