fix biocam chunk shape when channel_indexes is None

Author: alejoe91

neo/rawio/biocamrawio.py

@@ -112,9 +112,11 @@ def _get_analogsignal_chunk(self, block_index, seg_index, i_start, i_stop,
             i_start = 0
         if i_stop is None:
             i_stop = self._num_frames
-
         data = self._read_function(self._filehandle, i_start, i_stop, self._num_channels)
-        return data[:, channel_indexes]
+        if channel_indexes is None:
+            return data
+        else:
+            return data[:, channel_indexes]
 
 
 def open_biocam_file_header(filename):