Protect Qt console against SyntaxError from input transformers.

IPython/core/inputsplitter.py

@@ -535,8 +535,15 b' class IPythonInputSplitter(InputSplitter):'
         self.source_raw = ''
         self.transformer_accumulating = False
         self.within_python_line = False
+
+        last_exc = None
         for t in self.transforms:
-            t.reset()
+            try:
+                t.reset()
+            except SyntaxError as e:
+                last_exc = e
+        if last_exc is not None:
+            raise last_exc
     
     def flush_transformers(self):
         def _flush(transform, out):

IPython/qt/console/frontend_widget.py

@@ -204,8 +204,14 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
             prompt created. When triggered by an Enter/Return key press,
             'interactive' is True; otherwise, it is False.
         """
-        self._input_splitter.reset()
-        complete = self._input_splitter.push(source)
+        try:
+            self._input_splitter.reset()
+        except SyntaxError:
+            pass
+        try:
+            complete = self._input_splitter.push(source)
+        except SyntaxError:
+            return True
         if interactive:
             complete = not self._input_splitter.push_accepts_more()
         return complete
@@ -233,7 +239,10 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
         """
         # Flush all state from the input splitter so the next round of
         # reading input starts with a clean buffer.
-        self._input_splitter.reset()
+        try:
+            self._input_splitter.reset()
+        except SyntaxError:
+            pass
 
         if not self._reading:
             self._highlighter.highlighting_on = False