Revert "libobs: Check effect mutex exists before destroying it"

This reverts commit c2c47b1169b272498bdd6ffb1416f6d518200059.

libobs/graphics/graphics.c

@@ -213,8 +213,7 @@ void gs_destroy(graphics_t *graphics)
 	}
 
 	pthread_mutex_destroy(&graphics->mutex);
-	if (graphics->effect_mutex)
-		pthread_mutex_destroy(&graphics->effect_mutex);
+	pthread_mutex_destroy(&graphics->effect_mutex);
 	da_free(graphics->matrix_stack);
 	da_free(graphics->viewport_stack);
 	da_free(graphics->blend_state_stack);