Workaround for reload causing node spread (#7751)

#7435 introduced a tricky regression which will cause extremely small
levels of zoom with nodes spread far apart when in vue mode. I am able
to consistently reproduce this behaviour by
- Being in vue mode
- Swapping to a different tab so that ComfyUI is in the background
- Making a pointless line change to frontend code so that vite forces a
reload
- Waiting ~1 minute to ensure the reload completes
- Swapping back to the ComfyUI tab

From testing, if a reload occurs while the tab is backgrounded, the
canvas has an uninitialized size of 300x150. This PR proposes falling
back to a more sane default width and height of 1920x1080 if it is
detected that the canvas element is unitialized.

| Before | After |
| ------ | ----- |
| <img width="360" alt="before"
src="https://github.com/user-attachments/assets/8e19fc98-7187-4008-98cc-fb5ea3bcdce2"/>
| <img width="360" alt="after"
src="https://github.com/user-attachments/assets/add88614-3451-44df-ae9a-b0b867486459"
/>|

This appears to have consistently good results, but second opinions or
further testing would be appreciated. A more reasonable option (like
skipping this automatic fitView if the canvas has uninitialized size) is
likely to be safer, even if it results in a return of edge cases
resulting in a graph having no nodes in view after load.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7751-Workaround-for-reload-causing-node-spread-2d36d73d365081b9ae74d5f0e6f436f5)
by [Unito](https://www.unito.io)

src/lib/litegraph/src/DragAndScale.ts

@@ -192,8 +192,14 @@ export class DragAndScale {
     bounds: ReadOnlyRect,
     { zoom = 0.75 }: { zoom?: number } = {}
   ): void {
-    const cw = this.element.width / window.devicePixelRatio
-    const ch = this.element.height / window.devicePixelRatio
+    //If element hasn't initialized (browser tab is in background)
+    //it has a size of 300x150 and a more reasonable default is used instead.
+    const [width, height] =
+      this.element.width === 300 && this.element.height === 150
+        ? [1920, 1080]
+        : [this.element.width, this.element.height]
+    const cw = width / window.devicePixelRatio
+    const ch = height / window.devicePixelRatio
     let targetScale = this.scale
 
     if (zoom > 0) {