Fix crash in PolarizationEfficiencyCor algorithm for wrong input (#39921)

### Description of work
Details in issue #39832 
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If there is no linked issue provide context.
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Closes #39832. <!-- One line per closed issue. -->

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### To test:
Build the branch and check that this script throws an error but doesn't
crash Mantid ( while in the nightly does):

```
from mantid.simpleapi import *

names = []
for i in range(4):
    names.append(f'group_{i}')
    CreateWorkspace(DataX=np.linspace(0,5,6), DataY=[1]*5, OutputWorkspace=names[-1],Distribution=False, UnitX='Wavelength')
group = GroupWorkspaces(names)
ws=names[-1]
efficiencies= JoinISISPolarizationEfficiencies(F1=ws,F2=ws,P1=ws,P2=ws)
PolarizationEfficiencyCor(InputWorkspaces='group', OutputWorkspace='corr', Efficiencies=efficiencies)
```
_Added release notes_

Author: adriazalvarez

Framework/Algorithms/src/PolarizationEfficiencyCor.cpp

@@ -269,6 +269,13 @@ std::vector<std::string> PolarizationEfficiencyCor::getWorkspaceNameList() const
   std::vector<std::string> wsNames;
   if (!isDefault(Prop::INPUT_WORKSPACES)) {
     wsNames = getProperty(Prop::INPUT_WORKSPACES);
+    if (std::any_of(wsNames.cbegin(), wsNames.cend(), [](const auto &wsName) {
+          return AnalysisDataService::Instance().retrieveWS<MatrixWorkspace>(wsName) == nullptr;
+        })) {
+      throw std::invalid_argument(
+          "Only Matrix Workspaces can be added in InputWorkspace property list. If the input is a group, "
+          "use the InputWorkspaceGroup property");
+    }
   } else {
     WorkspaceGroup_sptr group = getProperty(Prop::INPUT_WORKSPACE_GROUP);
     auto const n = group->size();

Framework/Algorithms/test/PolarizationEfficiencyCorTest.h

@@ -95,6 +95,15 @@ class PolarizationEfficiencyCorTest : public CxxTest::TestSuite {
     alg->execute();
     checkOutputWorkspaceGroupSize(4);
   }
+
+  void test_input_ws_wildes_list_with_group_throws_error() {
+    auto alg = createAlgorithm(WILDES_METHOD, WILDES_METHOD);
+    (void)createWorkspaceGroup(4);
+    alg->setProperty("InputWorkspaces", "WS_GROUP_1");
+    // Error: InputWorkspaces property does not accept groups
+    TS_ASSERT_THROWS(alg->execute(), const std::invalid_argument &);
+  }
+
   void test_input_ws_frederikze_needs_group() {
     auto alg = createAlgorithm(FREDRIKZE_METHOD, FREDRIKZE_METHOD);
     alg->setProperty("InputWorkspaces", createWorkspacesInADS(4));

docs/source/release/v6.14.0/SANS/Bugfixes/39832.rst

@@ -0,0 +1 @@
+- Algorithm :ref:`algm-PolarizationEfficiencyCor` no longer crashes Mantid when using workspace groups in the ``InputWorkspaces`` property list.