Use sensible defaults in case TIOCGWINSZ fails (#224)

This can happen for example in embedded linux, in case
the application is started via serial terminal.

Signed-off-by: Jarosław Pelczar <jarek@jpelczar.com>
Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

src/ftxui/screen/terminal.cpp

@@ -33,8 +33,11 @@ Dimensions Terminal::Size() {
   return Dimensions{80, 80};
 
 #else
-  winsize w;
+  winsize w{};
   ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
+  if (w.ws_col == 0 || w.ws_row == 0) {
+    return Dimensions{80, 25};
+  }
   return Dimensions{w.ws_col, w.ws_row};
 #endif
 }