Fix logic for checking bin consistency in ConjoinWorkspaces algorithm

Framework/Algorithms/inc/MantidAlgorithms/ConjoinWorkspaces.h

@@ -55,6 +55,7 @@ class MANTID_ALGORITHMS_DLL ConjoinWorkspaces : public WorkspaceJoiners {
   void init() override;
   void exec() override;
 
+  bool checkBinning(const API::MatrixWorkspace_const_sptr &ws1, const API::MatrixWorkspace_const_sptr &ws2) const;
   void checkForOverlap(const API::MatrixWorkspace &ws1, const API::MatrixWorkspace &ws2, bool checkSpectra) const;
   API::MatrixWorkspace_sptr conjoinEvents(const DataObjects::EventWorkspace &ws1,
                                           const DataObjects::EventWorkspace &ws2);

Framework/Algorithms/src/ConjoinWorkspaces.cpp

@@ -61,9 +61,10 @@ void ConjoinWorkspaces::exec() {
     g_log.error(message);
     throw std::invalid_argument(message);
   }
-  // Check if bins match
+
+  // Check whether bins match
   bool checkBins = getProperty("CheckMatchingBins");
-  if (!WorkspaceHelpers::matchingBins(ws1, ws2) && checkBins) {
+  if (checkBins && !checkBinning(ws1, ws2)) {
     const std::string message("The bins do not match in the input workspaces. "
                               "Consider using RebinToWorkspace to preprocess "
                               "the workspaces before conjoining them.");
@@ -88,6 +89,24 @@ void ConjoinWorkspaces::exec() {
   AnalysisDataService::Instance().remove(getPropertyValue("InputWorkspace2"));
 }
 
+//----------------------------------------------------------------------------------------------
+/** Checks whether the binning is consistent between two workspaces
+ *  @param ws1 :: The first input workspace
+ *  @param ws2 :: The second input workspace
+ *  @return :: true if both workspaces have consistent binning.
+ */
+bool ConjoinWorkspaces::checkBinning(const API::MatrixWorkspace_const_sptr &ws1,
+                                     const API::MatrixWorkspace_const_sptr &ws2) const {
+  if (ws1->isRaggedWorkspace() || ws2->isRaggedWorkspace()) {
+    return false;
+  }
+
+  // If neither workspace is ragged, we only need to check the first specrum.
+  // Otherwise the matchingBins() function requires the two workspaces to have
+  // the same number of spectra.
+  return WorkspaceHelpers::matchingBins(ws1, ws2, true);
+}
+
 //----------------------------------------------------------------------------------------------
 /** Checks that the two input workspaces have non-overlapping spectra numbers
  * and contributing detectors