summary_graph.py: fix issue #360

Add try/except block around code accessing missing convolution
shape information.

distiller/summary_graph.py

@@ -325,8 +325,15 @@ class SummaryGraph(object):
             elif op['type'] == 'Gemm':
                 conv_out = op['outputs'][0]
                 conv_in = op['inputs'][0]
-                n_ifm = self.param_shape(conv_in)[1]
-                n_ofm = self.param_shape(conv_out)[1]
+                try:
+                    n_ifm = self.param_shape(conv_in)[1]
+                    n_ofm = self.param_shape(conv_out)[1]
+                    msglogger.error("An input to a Convolutional layer is missing shape information.")
+                    msglogger.error("For details see https://github.com/NervanaSystems/distiller/issues/360")
+                except IndexError:
+                    n_ifm = 0
+                    n_ofm = 0
+
                 # MACs = #IFM * #OFM
                 op['attrs']['MACs'] = n_ofm * n_ifm