PyCharm Jupyter Notebook debugger gives immediate "Debugger disconnected" once an external function raises an exception.

Hi, 

I noticed a problem when using PyCharm to debug a jupyter notebook. When an imported function raise an exception, the debugger will never attach until you restart the kernel.

To reproduce, create `crash.ipynb` in PyCharm with the following content 

#%%
from crash_func import crash
#%%
crash()
#%%

Also create a `crash.py`

def crash():
    raise ValueError()

When the `crash()` cell in the notebook is executed with debugger, it will run without problem for the first time. If you debug the cell again, the debugger prompts "Debugger disconnected" immediately without any extra information.

Screenshot is attached below. 

Environment Information:

Python version: Python 3.8.6
Installed packages:
Package                        Version
------------------------------ -------------------
ipykernel                      5.4.2
ipython                        7.19.0
ipython-genutils               0.2.0
ipywidgets                     7.6.3
jupyter                        1.0.0
jupyter-client                 6.1.11
jupyter-console                6.2.0
jupyter-core                   4.7.0
jupyterlab-pygments            0.1.2
jupyterlab-widgets             1.0.0
kiwisolver                     1.3.1
nbclient                       0.5.1
nbconvert                      6.0.7
nbformat                       5.1.2
notebook                       6.2.0
pip                            21.0
setuptools                     49.6.0.post20210108
tornado                        6.1
(irrelevant libraries were stripped out)

PyCharm information:

PyCharm 2020.3.3 (Professional Edition)
Build #PY-203.7148.72, built on January 26, 2021
Licensed to Yuanyi Wu
Subscription is active until December 27, 2021.
For educational use only.
Runtime version: 11.0.9.1+11-b1145.77 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Windows 10 10.0
GC: ParNew, ConcurrentMarkSweep
Memory: 1962M
Cores: 12
Registry: debugger.watches.in.variables=false
Non-Bundled Plugins: org.jetbrains.plugins.hocon, com.intellij.plugins.html.instantEditing, com.jetbrains.intellij.datalore , com.leinardi.pycharm.mypy, intellij-micropython, ru.meanmail.plugin.requirements