COMPMID-2855: NEReduceMean throws error for invalid configs

Change-Id: I600507d0de19d7da6c1a13edcfff0a11ea6b5264
Signed-off-by: Pablo Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/2254
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Reviewed-by: Giorgio Arena <giorgio.arena@arm.com>
Reviewed-by: Giuseppe Rossini <giuseppe.rossini@arm.com>
Reviewed-by: Michalis Spyrou <michalis.spyrou@arm.com>
Reviewed-by: Manuel Bottini <manuel.bottini@arm.com>
Reviewed-by: SiCong Li <sicong.li@arm.com>
diff --git a/arm_compute/runtime/NEON/functions/NEReduceMean.h b/arm_compute/runtime/NEON/functions/NEReduceMean.h
index 9df71f2..6fbd72b 100644
--- a/arm_compute/runtime/NEON/functions/NEReduceMean.h
+++ b/arm_compute/runtime/NEON/functions/NEReduceMean.h
@@ -71,7 +71,7 @@
     std::vector<NEReductionOperation> _reduction_kernels;
     std::vector<Tensor>               _reduced_outs;
     NEReshapeLayer                    _reshape;
-    unsigned int                      _reduction_ops;
+    int                               _reduction_ops;
     bool                              _keep_dims;
 };
 } // namespace arm_compute