[Flang][OpenMP] Fix issue with empty critical or critical without surrounding context (#71944)

Add the sourcerange for critical directive.

Fixes #65571

Author: kiranchandramohan

flang/lib/Semantics/resolve-names.cpp

@@ -1459,6 +1459,20 @@ class OmpVisitor : public virtual DeclarationVisitor {
   void Post(const parser::OmpEndSectionsDirective &) {
     messageHandler().set_currStmtSource(std::nullopt);
   }
+  bool Pre(const parser::OmpCriticalDirective &x) {
+    AddOmpSourceRange(x.source);
+    return true;
+  }
+  void Post(const parser::OmpCriticalDirective &) {
+    messageHandler().set_currStmtSource(std::nullopt);
+  }
+  bool Pre(const parser::OmpEndCriticalDirective &x) {
+    AddOmpSourceRange(x.source);
+    return true;
+  }
+  void Post(const parser::OmpEndCriticalDirective &) {
+    messageHandler().set_currStmtSource(std::nullopt);
+  }
 };
 
 bool OmpVisitor::NeedsScope(const parser::OpenMPBlockConstruct &x) {

flang/test/Semantics/OpenMP/critical-empty.f90

@@ -0,0 +1,6 @@
+! RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp 
+! Test that there are no errors for an empty critical construct
+
+!$omp critical
+!$omp end critical
+end