Fix calling pvPortMalloc on FreeRTOS with size zero resulting in vApplicationMallocFailedHook getting called and FreeRTOS asserting

Author: Thom747

erpc_c/port/erpc_port_freertos.cpp

@@ -55,6 +55,10 @@ void operator delete[](void *ptr) THROW
 
 void *erpc_malloc(size_t size)
 {
+    if (size == 0)
+    {
+        return nullptr;
+    }
     void *p = pvPortMalloc(size);
     return p;
 }