bug-fix: Numpy ValueError when cheking empty list equality

Using the equality operator with an empty list will result in the
following error.

ValueError: operands could not be broadcast together with shapes (28,) (0,)

Using len() and inverting the logic avoids this issue.

Author: ajadczaksunriselabs

wfdb/io/annotation.py

@@ -940,10 +940,10 @@ def wr_ann_file(self, write_fs, write_dir=""):
         core_bytes = self.calc_core_bytes()
 
         # Mark the end of the special annotation types if needed
-        if fs_bytes == [] and cl_bytes == []:
-            end_special_bytes = []
-        else:
+        if len(fs_bytes) or len(cl_bytes):
             end_special_bytes = [0, 236, 255, 255, 255, 255, 1, 0]
+        else:
+            end_special_bytes = []
 
         # Write the file
         with open(