Fixed issues found by static analysis (mostly DBZ)

modules/ml/src/em.cpp

@@ -616,6 +616,7 @@ public:
             expDiffSum += v; // sum_j(exp(L_ij - L_iq))
         }
 
+        CV_Assert(expDiffSum > 0);
         if(probs)
             L.convertTo(*probs, ptype, 1./expDiffSum);
 

modules/ml/src/rtrees.cpp

@@ -170,6 +170,7 @@ public:
                 double val = std::abs(w->ord_responses[w->sidx[i]]);
                 max_response = std::max(max_response, val);
             }
+            CV_Assert(fabs(max_response) > 0);
         }
 
         if( rparams.calcVarImportance )

modules/ml/src/tree.cpp

@@ -630,7 +630,7 @@ void DTreesImpl::calcValue( int nidx, const vector<int>& _sidx )
                 w->cv_Tn[nidx*cv_n + j] = INT_MAX;
             }
         }
-
+        CV_Assert(fabs(sumw) > 0);
         node->node_risk = sum2 - (sum/sumw)*sum;
         node->node_risk /= sumw;
         node->value = sum/sumw;