Always update unconsumed tail

Author: rhpvorderman

src/isal/isal_zlib.pyx

@@ -556,17 +556,18 @@ cdef class Decompress:
     cdef save_unconsumed_input(self, Py_buffer *data):
         cdef Py_ssize_t old_size, new_size, left_size
         cdef bytes new_data
-        left_size = <unsigned char*>data.buf + data.len - self.stream.next_in
-        new_data = PyBytes_FromStringAndSize(<char *>self.stream.next_in, left_size)
+        if self.stream.avail_in > 0:
+            left_size = <unsigned char*>data.buf + data.len - self.stream.next_in
+            new_data = PyBytes_FromStringAndSize(<char *>self.stream.next_in, left_size)
+        else:
+            new_data = b""
         if self.stream.block_state == ISAL_BLOCK_FINISH:
             self.eof = 1
-            if self.stream.avail_in > 0 or self._view_bitbuffer():
-                # The block is finished and this decompressobject can not be
-                # used anymore. Some unused data is in the bitbuffer and has to
-                # be recovered.
-                self.unused_data = self._view_bitbuffer() +  new_data
-        if self.stream.avail_in > 0:
-            self.unconsumed_tail = new_data
+            # The block is finished and this decompressobject can not be
+            # used anymore. Some unused data is in the bitbuffer and has to
+            # be recovered.
+            self.unused_data = self._view_bitbuffer() +  new_data
+        self.unconsumed_tail = new_data
 
     def decompress(self, data, Py_ssize_t max_length = 0):
         """