Fix bug where image viewer could overflow vertically on Send page

This doesn't happen on the View page, but just because we allow
unlimited height - on the Send page the layout doesn't work that way.

Author: pimterry

src/components/editor/image-viewer.tsx

@@ -14,6 +14,7 @@ export const ImageViewer = styled((p: {
 />)`
     display: block;
     max-width: 100%;
+    max-height: 100%;
     margin: 0 auto;
     object-fit: scale-down;
 `;