Chore (Windows): silence some warnings

src/common/io/io_windows.c

@@ -266,14 +266,20 @@ const char* ffGetTerminalResponse(const char* request, int nParams, const char*
     {
         DWORD bytes = 0;
         if (!ReadFile(hInput, buffer, sizeof(buffer) - 1, &bytes, NULL) || bytes == 0)
+        {
+            va_end(args);
             return "ReadFile() failed";
+        }
 
         bytesRead += bytes;
         buffer[bytesRead] = '\0';
 
         int ret = vsscanf(buffer, format, args);
         if (ret <= 0)
+        {
+            va_end(args);
             return "vsscanf(buffer, format, args) failed";
+        }
         if (ret >= nParams)
             break;
     }