Create a QApplication for inputhook if one doesn't already exist

Closes gh-9784

IPython/terminal/pt_inputhooks/qt.py

@@ -1,10 +1,15 b''
 import sys
 from IPython.external.qt_for_kernel import QtCore, QtGui
 
+# If we create a QApplication, keep a reference to it so that it doesn't get
+# garbage collected.
+_appref = None
+
 def inputhook(context):
+    global _appref
     app = QtCore.QCoreApplication.instance()
     if not app:
-        return
+        _appref = app = QtGui.QApplication([" "])
     event_loop = QtCore.QEventLoop(app)
 
     if sys.platform == 'win32':