Fix crash in GpuGemv.perform with zero-size inputs

theano/gpuarray/blas.py

@@ -73,8 +73,12 @@ class GpuGemv(BlasOp):
         inplace = self.inplace
         if inplace and y.strides[0] < 0:
             inplace = False
-        out_storage[0][0] = blas.gemv(alpha, A, x, beta, y,
-                                      overwrite_y=inplace)
+        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)
 
     def c_code(self, node, name, inp, out, sub):
         vars = dict(out=out[0], y=inp[0], alpha=inp[1], A=inp[2], x=inp[3],