Fix BufferedReader.read1 leaving object in reentrant state on error

BufferedReader.read1() could leave the buffered object in a
reentrant (locked) state when an exception was raised while
allocating the output buffer.

This change ensures the internal buffered lock is always released
on error, keeping the object in a consistent state after failures.

Signed-off-by: Yongtao Huang <yongtaoh2022@gmail.com>

Author: hyongtao-code

Modules/_io/bufferedio.c

@@ -1073,6 +1073,7 @@ _io__Buffered_read1_impl(buffered *self, Py_ssize_t n)
 
     PyBytesWriter *writer = PyBytesWriter_Create(n);
     if (writer == NULL) {
+        LEAVE_BUFFERED(self)
         return NULL;
     }