Merge pull request #861 from yangfei963158659/develop

repair bug of bias is nullptr

src/operators/math/gemm.cpp

@@ -2809,10 +2809,15 @@ void Sgemm(int m, int n, int k, float alpha, const float *A, int lda,
 #else
       PackMatrixA_6r(mc, KC, mc % MR, &A(i, 0), lda, packedA);
 #endif
+      if (bias == nullptr) {
+        InnerKernelWithBias(mc, nc, alpha, packedA, packedB, beta, packedC,
+                            &C(i, j), ldc, relu, nullptr);
+      } else {
         InnerKernelWithBias(mc, nc, alpha, packedA, packedB, beta, packedC,
                             &C(i, j), ldc, relu, bias + i);
       }
     }
+  }
 
   paddle_mobile::memory::Free(packedA);
   paddle_mobile::memory::Free(packedB);