Fixed several issues found by static analysis

Author: mshabunin

modules/calib3d/src/sqpnp.hpp

@@ -72,6 +72,7 @@ class PoseSolver {
         cv::Matx<double, 9, 1> r_hat;
         cv::Matx<double, 3, 1> t;
         double sq_error;
+        SQPSolution() : sq_error(0) {}
     };
 
     /*

modules/dnn/src/layers/pooling_layer.cpp

@@ -750,7 +750,7 @@ virtual Ptr<BackendNode> initNgraph(const std::vector<Ptr<BackendWrapper> >& inp
                             if (max_elem!=last)
                             {
                                 dstData[x0] = *max_elem;
-                                if( compMaxIdx )
+                                if( compMaxIdx && dstMaskData )
                                 {
                                     dstMaskData[x0] = std::distance(first, max_elem);
                                 }

modules/videoio/src/cap_msmf.cpp

@@ -309,7 +309,7 @@ class SourceReaderCB : public IMFSourceReaderCallback
 {
 public:
     SourceReaderCB() :
-        m_nRefCount(0), m_hEvent(CreateEvent(NULL, FALSE, FALSE, NULL)), m_bEOS(FALSE), m_hrStatus(S_OK), m_reader(NULL), m_dwStreamIndex(0)
+        m_nRefCount(0), m_hEvent(CreateEvent(NULL, FALSE, FALSE, NULL)), m_bEOS(FALSE), m_hrStatus(S_OK), m_reader(NULL), m_dwStreamIndex(0), m_lastSampleTimestamp(0)
     {
     }