[Coverity Scan] sample issue from CS fix (#12509)

Signed-off-by: xuejun <Xuejun.Zhai@intel.com>

Signed-off-by: xuejun <Xuejun.Zhai@intel.com>
Co-authored-by: River Li <river.li@intel.com>

samples/c/common/opencv_c_wrapper/opencv_c_wrapper.cpp

@@ -12,6 +12,7 @@ extern "C" {
 
 int image_read(const char* img_path, c_mat_t* img) {
     BitMap bmp;
+    bmp.data = NULL;
     int retCode = readBmpImage(img_path, &bmp);
 
     img->mat_data = bmp.data;