Fix crash in GpuGemv.perform with zero-size inputs

theano/gpuarray/blas.py

@@ -73,6 +73,10 @@ class GpuGemv(BlasOp):
         inplace = self.inplace
         if inplace and y.strides[0] < 0:
             inplace = False
+        if A.shape[1] == 0:
+            out_storage[0][0] = pygpu.zeros(y.shape, dtype=y.dtype,
+                                            context=y.context)
+        else:
             out_storage[0][0] = blas.gemv(alpha, A, x, beta, y,
                                           overwrite_y=inplace)