Merge pull request #4150 from silx-kit/fix_opencl_convolution_cpu

`silx.opencl.convolution`: Fixed separable convolution on CPU that crashed in some cases

src/silx/opencl/convolution.py

@@ -385,6 +385,8 @@ def _batched_convolution(self, axis, input_ref=None, output_ref=None):
             self.kernel_args, input_ref, output_ref
         )
         ev = opencl_kernel(*opencl_kernel_args)
+        if self.queue.device.type == cl.device_type.CPU:
+            ev.wait()
         if self.profile:
             self.events.append(EventDescription("batched convolution", ev))