Destroy screen once stream is finished

The screen receives callbacks from the decoder, fed by the stream.

The decoder is run from the stream thread, so waiting for the end of
stream is sufficient to avoid possible use-after-destroy.

app/src/scrcpy.c

@@ -430,10 +430,6 @@ scrcpy(const struct scrcpy_options *options) {
     LOGD("quit...");
 
 end:
-    if (screen_initialized) {
-        screen_destroy(&screen);
-    }
-
     // stop stream and controller so that they don't continue once their socket
     // is shutdown
     if (stream_started) {
@@ -459,6 +455,13 @@ end:
     if (stream_started) {
         stream_join(&stream);
     }
+
+    // Destroy the screen only after the stream is guaranteed to be finished,
+    // because otherwise the screen could receive new frames after destruction
+    if (screen_initialized) {
+        screen_destroy(&screen);
+    }
+
     if (controller_started) {
         controller_join(&controller);
     }