Prevent usage of hard-coded string for contentDescription, and fix existing issues.

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/components/EditableAvatarView.kt

@@ -87,7 +87,7 @@ fun EditableAvatarView(
                 Icon(
                     modifier = Modifier.size(16.dp),
                     resourceId = CommonDrawables.ic_edit,
-                    contentDescription = "",
+                    contentDescription = null,
                     tint = MaterialTheme.colorScheme.onPrimary,
                 )
             }

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/components/UnresolvedUserRow.kt

@@ -79,7 +79,7 @@ fun UnresolvedUserRow(
             ) {
                 Icon(
                     resourceId = CommonDrawables.ic_compound_error,
-                    contentDescription = "",
+                    contentDescription = null,
                     modifier = Modifier
                         .size(18.dp)
                         .align(Alignment.Top)

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/components/UnsavedAvatar.kt

@@ -72,7 +72,7 @@ fun UnsavedAvatar(
         Box(modifier = commonModifier.background(ElementTheme.colors.temporaryColorBgSpecial)) {
             Icon(
                 imageVector = Icons.Outlined.AddAPhoto,
-                contentDescription = "",
+                contentDescription = null,
                 modifier = Modifier
                     .align(Alignment.Center)
                     .size(40.dp),