unittest: fix ATCmdParser test segfault

[maciejbocianski]

Summary of changes

Fixes ATCmdParser unittest bug (causing segfault when run unittests on windows)

53: Test command: C:\Users\macboc01.ARM\work\mbed\dev\mbed-os\BUILD\unittests\platform-ATCmdParser.exe
53: Test timeout computed to be: 1500
53: Running main() from gmock_main.cc
53: [==========] Running 13 tests from 1 test case.
53: [----------] Global test environment set-up.
53: [----------] 13 tests from test_ATCmdParser
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_create
53: [       OK ] test_ATCmdParser.test_ATCmdParser_create (0 ms)
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_set_timeout
53: [       OK ] test_ATCmdParser.test_ATCmdParser_set_timeout (0 ms)
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_process_oob
53: [       OK ] test_ATCmdParser.test_ATCmdParser_process_oob (0 ms)
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_flush
53: [       OK ] test_ATCmdParser.test_ATCmdParser_flush (0 ms)
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_write
53: [       OK ] test_ATCmdParser.test_ATCmdParser_write (0 ms)
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_set_delimiter
53: [       OK ] test_ATCmdParser.test_ATCmdParser_set_delimiter (0 ms)
53: [ RUN      ] test_ATCmdParser.test_ATCmdParser_read
1/1 Test #53: platform-ATCmdParser .............***Exception: SegFault  1.26 sec

0% tests passed, 1 tests failed out of 1

Total Test time (real) =   1.28 sec

The following tests FAILED:
         53 - platform-ATCmdParser (SEGFAULT)
Errors while running CTest
mingw32-make: *** [Makefile:61: test] Error 8

Impact of changes

Migration actions required

Documentation

---

Pull request type

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

---

Test results

[] No Tests required for this change (E.g docs only update)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

---

Reviewers

@jamesbeyond

---

[jamesbeyond]

LGTM

[mbed-ci]

Test run: SUCCESS

Summary: 1 of 1 test jobs passed
Build number : 1
Build artifacts

[0xc0170]

Fixes ATCmdParser unittest bug (causing segfault when run unittests on windows)

Thus we did not see this one in CI here.

[maciejbocianski]

Fixes ATCmdParser unittest bug (causing segfault when run unittests on windows)

Thus we did not see this one in CI here.

Exactly