Merge pull request #92 from hoshino111/2d_minimise

Fix crash while minimizing window with ui camera

Author: DJMcNab

crates/bevy_ui/src/render/render_pass.rs

@@ -66,10 +66,11 @@ impl Node for UiPassNode {
         world: &World,
     ) -> Result<(), NodeRunError> {
         let view_entity = graph.get_input_entity(Self::IN_VIEW)?;
-        let (transparent_phase, target) = self
-            .query
-            .get_manual(world, view_entity)
-            .expect("view entity should exist");
+        // If there is no view entity, do not try to process the render phase for the view
+        let (transparent_phase, target) = match self.query.get_manual(world, view_entity) {
+            Ok(it) => it,
+            _ => return Ok(()),
+        };
         let pass_descriptor = RenderPassDescriptor {
             label: Some("ui_pass"),
             color_attachments: &[RenderPassColorAttachment {