fix(shell): memory free error.

source/dnode/mgmt/exe/dmMain.c

@@ -68,6 +68,7 @@ static void dmSetSignalHandle() {
 
 static int32_t dmParseArgs(int32_t argc, char const *argv[]) {
   int32_t cmdEnvIndex = 0;
+  if (argc < 2) return 0;
   global.envCmd = taosMemoryMalloc(argc-1);
   memset(global.envCmd, 0, argc-1);
   for (int32_t i = 1; i < argc; ++i) {

source/os/src/osMemory.c

@@ -82,6 +82,8 @@ int32_t taosBackTrace(void **buffer, int32_t size) {
 #endif
 
 void *taosMemoryMalloc(int32_t size) {
+  if (size == 0) return NULL;
+  
 #ifdef USE_TD_MEMORY
   void *tmp = malloc(size + sizeof(TdMemoryInfo));
   if (tmp == NULL) return NULL;