Emscripten: Added missing error messages for audio and joystick init failures.

src/audio/emscripten/SDL_emscriptenaudio.c

@@ -263,6 +263,10 @@ Emscripten_Init(SDL_AudioDriverImpl * impl)
         return 0;
     });
 
+    if (!available) {
+        SDL_SetError("No audio context available");
+    }
+
     return available;
 }
 

src/joystick/emscripten/SDL_sysjoystick.c

@@ -200,6 +200,7 @@ SDL_SYS_JoystickInit(void)
 
     /* Check if gamepad is supported by browser */
     if (numjs == EMSCRIPTEN_RESULT_NOT_SUPPORTED) {
+        SDL_SetError("Gamepads not supported");
         return -1;
     }
 
@@ -221,6 +222,7 @@ SDL_SYS_JoystickInit(void)
 
     if(retval != EMSCRIPTEN_RESULT_SUCCESS) {
         SDL_SYS_JoystickQuit();
+        SDL_SetError("Could not set gamepad connect callback");
         return -1;
     }
 
@@ -229,6 +231,7 @@ SDL_SYS_JoystickInit(void)
                                                          Emscripten_JoyStickDisconnected);
     if(retval != EMSCRIPTEN_RESULT_SUCCESS) {
         SDL_SYS_JoystickQuit();
+        SDL_SetError("Could not set gamepad disconnect callback");
         return -1;
     }