refs #10208. Fix issues raised in testing.

Code/Mantid/Framework/Algorithms/src/LorentzCorrection.cpp

@@ -119,12 +119,20 @@ namespace Mantid
           continue;
 
         const double twoTheta = inWS->detectorTwoTheta(detector);
+        const double sinTheta = std::sin(twoTheta / 2);
+        double sinThetaSq = sinTheta * sinTheta;
 
         for (size_t j = 0; j < inY.size(); ++j)
         {
           const double wL = isHist ? (0.5 * (inX[j] + inX[j + 1])) : inX[j];
-          double sinTheta = std::sin(twoTheta / 2);
-          double weight = sinTheta * sinTheta / (wL * wL * wL * wL);
+          if(wL == 0)
+          {
+            std::stringstream buffer;
+            buffer << "Cannot have zero values Wavelength. At workspace index: " << i; 
+            throw std::runtime_error(buffer.str());
+          }
+          
+          double weight = sinThetaSq / (wL * wL * wL * wL);
           outY[j] *= weight;
           outE[j] *= weight;
         }

Code/Mantid/Framework/Algorithms/test/LorentzCorrectionTest.h

@@ -115,6 +115,20 @@ public:
         alg.setProperty("InputWorkspace", ws_tof), std::invalid_argument&);
   }
 
+  void test_throws_if_wavelength_zero()
+  {
+    auto ws_lam = this->create_workspace(2 /*nBins*/);
+    ws_lam->dataX(0)[0] = 0; // Make wavelength zero
+    ws_lam->dataX(0)[1] = 0; // Make wavelength zero
+    LorentzCorrection alg;
+    alg.setChild(true);
+    alg.setRethrows(true);
+    alg.initialize();
+    alg.setProperty("InputWorkspace", ws_lam);
+    alg.setPropertyValue("OutputWorkspace", "temp");
+    TSM_ASSERT_THROWS("Should throw with zero wavelength values.", alg.execute(), std::runtime_error&);
+  }
+
   void test_execute()
   {
     auto ws_lam = this->create_workspace(2 /*nBins*/);