FP invalidFunctionArgStr

[chrchr]

From ocproxy-1.60/contrib/ports/old/coldfire/sys_arch.c:

void f(int num_thread) {
	char thread_name[8] = "        ";
	num_thread = (num_thread +1) % 100;
	sprintf(thread_name, "lwip%02d", num_thread);
	thread_name[strlen(thread_name)] = ' ';
}

test.cpp:6:24: error: Invalid strlen() argument nr 1. A nul-terminated string is required. [invalidFunctionArgStr]
    thread_name[strlen(thread_name)] = ' ';
                       ^

The string is no longer null-terminated after the last line, but still is when strlen() is called.
Tested with ​https://github.com/danmar/cppcheck/commit/b51aea5531a1eeb49f6dad160142312186e375bc.

[chrchr]

Fixed by ​https://github.com/danmar/cppcheck/pull/4264