Handle null projection properly if provider app op is not enabled.

                // We do not call ContentProvider#query with a modified where clause since

                // We do not call ContentProvider#query with a modified where clause since

                // the implementation is not guaranteed to be backed by a SQL database, hence

                // the implementation is not guaranteed to be backed by a SQL database, hence

                // it may not handle properly the tautology where clause we would have created.

                // it may not handle properly the tautology where clause we would have created.

                if (projection != null) {

                    return new MatrixCursor(projection, 0);

                    return new MatrixCursor(projection, 0);

                }

                }

                // Null projection means all columns but we have no idea which they are.

                // However, the caller may be expecting to access them my index. Hence,

                // we have to execute the query as if allowed to get a cursor with the

                // columns. We then use the column names to return an empty cursor.

                Cursor cursor = ContentProvider.this.query(uri, projection, selection,

                        selectionArgs, sortOrder, CancellationSignal.fromTransport(

                                cancellationSignal));

                // Create a projection for all columns.

                final int columnCount = cursor.getCount();

                String[] allColumns = new String[columnCount];

                for (int i = 0; i < columnCount; i++) {

                    allColumns[i] = cursor.getColumnName(i);

                }

                // Return an empty cursor for all columns.

                return new MatrixCursor(allColumns, 0);

            }

            final String original = setCallingPackage(callingPkg);

            final String original = setCallingPackage(callingPkg);

            try {

            try {

                return ContentProvider.this.query(

                return ContentProvider.this.query(