fix coverity reports

modules/dnn/src/dnn.cpp

@@ -1801,7 +1801,7 @@ struct Net::Impl
                         nextEltwiseLayer = nextData->layerInstance.dynamicCast<EltwiseLayer>();
 
                     if( !nextEltwiseLayer.empty() && pinsToKeep.count(lpNext) == 0 &&
-                        nextData->inputBlobsId.size() == 2 )
+                        nextData && nextData->inputBlobsId.size() == 2 )
                     {
                         LayerData *eltwiseData = nextData;
 

modules/videoio/src/cap_v4l.cpp

@@ -348,7 +348,9 @@ struct CvCaptureCAM_V4L CV_FINAL : public CvCapture
 /***********************   Implementations  ***************************************/
 
 CvCaptureCAM_V4L::CvCaptureCAM_V4L() : deviceHandle(-1), bufferIndex(-1)
-{}
+{
+    memset(&timestamp, 0, sizeof(timestamp));
+}
 
 CvCaptureCAM_V4L::~CvCaptureCAM_V4L() {
     streaming(false);
@@ -1739,7 +1741,6 @@ double CvCaptureCAM_V4L::getProperty(int property_id) const
         return  value;
     }
     }
-    return -1.0;
 }
 
 bool CvCaptureCAM_V4L::icvSetFrameSize(int _width, int _height)