fix: handle invalid GIF dimensions gracefully

Fix NaN aspectRatio when rehydrating GIFs from drafts by:

1. Adding validation in parseTenorGif to reject invalid dimensions
   (NaN, zero, or negative values)
2. Adding defensive checks in GifEmbed to fallback to 1:1 aspect
   ratio if dimensions are invalid
3. Adding defensive checks in composer ExternalEmbedGif to fallback
   to 16:9 if gif.media_formats.gif.dims is missing or invalid

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Post/Embed/ExternalEmbed/Gif.tsx

@@ -114,11 +114,10 @@ export function GifEmbed({
 
   let aspectRatio = 1
   if (params.dimensions) {
-    aspectRatio = clamp(
-      params.dimensions.width / params.dimensions.height,
-      0.75,
-      4,
-    )
+    const ratio = params.dimensions.width / params.dimensions.height
+    if (!isNaN(ratio) && isFinite(ratio)) {
+      aspectRatio = clamp(ratio, 0.75, 4)
+    }
   }
 
   return (

src/lib/strings/embed-player.ts

@@ -558,6 +558,16 @@ export function parseTenorGif(urlp: URL):
     width: Number(w),
   }
 
+  // Validate dimensions are valid positive numbers
+  if (
+    isNaN(dimensions.height) ||
+    isNaN(dimensions.width) ||
+    dimensions.height <= 0 ||
+    dimensions.width <= 0
+  ) {
+    return {success: false}
+  }
+
   if (IS_WEB) {
     if (IS_WEB_SAFARI) {
       id = id.replace('AAAAC', 'AAAP1')

src/view/com/composer/ExternalEmbed.tsx

@@ -37,7 +37,13 @@ export const ExternalEmbedGif = ({
   )
 
   const loadingStyle: ViewStyle = {
-    aspectRatio: gif.media_formats.gif.dims[0] / gif.media_formats.gif.dims[1],
+    aspectRatio: (() => {
+      const dims = gif.media_formats.gif?.dims
+      if (dims && dims[0] > 0 && dims[1] > 0) {
+        return dims[0] / dims[1]
+      }
+      return 16 / 9 // Default aspect ratio
+    })(),
     width: '100%',
   }