fix: don't report expo-image disk-cache misses for photo storage size (#1951)

getExpoImageStorageSize threw when expo-image's getCachePathAsync
returned null (a benign disk-cache miss), and the only caller reported it
to Sentry (COMAPEO-20Z).

Return number | null and treat null as 'no storage size' in
useImageLoadInfo. UI is unchanged (the label was already optional).

Making the label always show needs the blob server to send
Content-Length: comapeo-core#1281 + #1945.

Fixes COMAPEO-20Z.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: gmaclennan

src/frontend/lib/file-system.ts

@@ -65,24 +65,22 @@ export async function selectFile({
  */
 export async function getExpoImageStorageSize(
   imageURL: string,
-): Promise<number> {
+): Promise<number | null> {
   let fileInfo: FileSystem.FileInfo;
 
   if (imageURL.startsWith('file://')) {
     fileInfo = await FileSystem.getInfoAsync(imageURL);
   } else {
     const cachePath = await ExpoImage.getCachePathAsync(imageURL);
 
-    if (!cachePath) {
-      throw new Error(`Could not get size for image at ${imageURL}`);
-    }
+    // null when the image isn't in expo-image's disk cache (served from memory,
+    // not yet written, or evicted) — a benign miss, not an error.
+    if (!cachePath) return null;
 
     fileInfo = await FileSystem.getInfoAsync(`file://${cachePath}`);
   }
 
-  if (!fileInfo.exists) {
-    throw new Error(`Could not get size for image at ${imageURL}`);
-  }
+  if (!fileInfo.exists) return null;
 
   return fileInfo.size;
 }

src/frontend/screens/PhotoPreviewModal/helpers.ts

@@ -194,7 +194,7 @@ export function useImageLoadInfo() {
       setImageLoadInfo({
         height: event.source.height,
         width: event.source.width,
-        storageSize,
+        storageSize: storageSize ?? undefined,
       });
     } catch (err) {
       captureException(err);