Update sql_magic.py

Author: HuilinWu2

python/openmldb/sql_magic/sql_magic.py

@@ -44,6 +44,7 @@ def sql(self, line, cell=None):
             print("Success to execute sql")
 
 def register(db, test=False):
+    global get_ipython
     if test:
         from IPython.testing.globalipapp import get_ipython
     ip = get_ipython()