Fix blank page when loading pages with no lines

Handle pages without lines in updateTranscriptionImages by still loading and displaying the canvas even when there are no line annotations. Shows the full page image instead of returning early.

Co-authored-by: cubap <1119165+cubap@users.noreply.github.com>

Author: Copilot

interfaces/transcription/index.js

@@ -518,7 +518,21 @@ export default class TranscriptionInterface extends HTMLElement {
     const { orderedItems, columnsInPage } = orderPageItemsByColumns(projectPage, this.#page)
     this.#page.items = orderedItems
     let thisLine = this.#page.items?.[0]
-    if (!thisLine) return
+    
+    // Handle pages with no lines - still load the canvas
+    if (!thisLine) {
+      // Get canvas from page target even when there are no lines
+      const { canvasID } = this.setCanvasAndSelector(null, this.#page)
+      if (!canvasID) return
+      const canvas = this.#canvas = await vault.get(canvasID, 'canvas')
+      // Show full page when there are no lines
+      const regionValue = `0,0,${canvas?.width ?? 'full'},${(canvas?.height && canvas?.height / 10) ?? 120}`
+      topImage.canvas = canvasID
+      bottomImage.canvas = canvas
+      topImage.setAttribute('region', regionValue)
+      return
+    }
+    
     if (!(thisLine?.body)) thisLine = await vault.get(thisLine, 'annotation', true)
     const { canvasID, region } = this.setCanvasAndSelector(thisLine, this.#page)
     const canvas = this.#canvas = await vault.get(canvasID, 'canvas')