[C-libcurl] Guard memory free for query parameters to avoid coredump

Created by: ityuhui

After generating a C-libcurl client for kubernetes and linking with my program, a coredump will happen due to deleting an un-allocated memory

Program received signal SIGSEGV, Segmentation fault.
__GI___libc_free (mem=0x3000000030) at malloc.c:2951
2951    malloc.c: No such file or directory.
(gdb) bt
#0  __GI___libc_free (mem=0x3000000030) at malloc.c:2951
#1  0x00000000004290a0 in CoreV1API_listCoreV1NamespacedSecret (apiClient=0x6b4570, namespace=0x488489 "default", 
    pretty=0x0, allowWatchBookmarks=0, _continue=0x0, fieldSelector=0x0, labelSelector=0x0, limit=0, 
    resourceVersion=0x0, timeoutSeconds=1000, watch=0) at /root/c_k8s_api_client/api/CoreV1API.c:16598
#2  0x0000000000401532 in listSecret () at main.c:77
#3  0x000000000040179f in main (argc=2, argv=0x7fffffffe0a8) at main.c:159

The coredump happens at:

    free(keyQuery_pretty);

But actually, keyQuery_pretty is not allocated.

So I added some guards for the query parameters before memory free.

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