fixed client-reported crashes in the pdf viewer, image picker and prosemirror images, mapped webdav errors to user messages and hardened keychain, cache and push stores against io failures

lib/widget/prosemirror/pm_image_view.dart

@@ -42,7 +42,7 @@ class PmImageView extends StatelessWidget {
         final available = constraints.maxWidth.isFinite
             ? constraints.maxWidth
             : MediaQuery.sizeOf(context).width;
-        final targetWidth = _resolveWidth(node.width, available);
+        final targetWidth = resolvePmImageWidth(node.width, available);
 
         Widget image = ConstrainedBox(
           constraints: BoxConstraints(maxWidth: targetWidth ?? available),
@@ -121,16 +121,20 @@ class PmImageView extends StatelessWidget {
     }
   }
 
-  double? _resolveWidth(String? width, double available) {
-    if (width == null) return null;
-    final length = parsePmCssLength(width);
-    if (length == null) return null;
-    final value = length.value;
-    final resolved = switch (length.unit) {
-      '%' => available * value / 100,
-      'em' || 'rem' => value * 16,
-      _ => value,
-    };
-    return resolved.clamp(1, available);
-  }
+}
+
+/// Resolves a CSS `width` attribute against [available] pixels, or `null` when
+/// the image should simply fill what it gets. Layout may hand out zero width
+/// mid-animation, which would otherwise invert the clamp bounds.
+double? resolvePmImageWidth(String? width, double available) {
+  if (width == null || available < 1) return null;
+  final length = parsePmCssLength(width);
+  if (length == null) return null;
+  final value = length.value;
+  final resolved = switch (length.unit) {
+    '%' => available * value / 100,
+    'em' || 'rem' => value * 16,
+    _ => value,
+  };
+  return resolved.clamp(1, available);
 }