[Flang][OpenMP] Fix a crash for declare target in an interface (#117709)

This is a point fix for the crash in #116426. Leaving the bug open to
further explore declare target issues for interfaces.

Author: kiranchandramohan

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -487,13 +487,15 @@ static void getDeclareTargetInfo(
   } else if (const auto *clauseList{
                  parser::Unwrap<parser::OmpClauseList>(spec.u)}) {
     List<Clause> clauses = makeClauses(*clauseList, semaCtx);
-    if (clauses.empty() &&
-        (!eval.getOwningProcedure()->isMainProgram() ||
-         eval.getOwningProcedure()->getMainProgramSymbol())) {
-      // Case: declare target, implicit capture of function
-      symbolAndClause.emplace_back(
-          mlir::omp::DeclareTargetCaptureClause::to,
-          eval.getOwningProcedure()->getSubprogramSymbol());
+    if (clauses.empty()) {
+      Fortran::lower::pft::FunctionLikeUnit *owningProc =
+          eval.getOwningProcedure();
+      if (owningProc && (!owningProc->isMainProgram() ||
+                         owningProc->getMainProgramSymbol())) {
+        // Case: declare target, implicit capture of function
+        symbolAndClause.emplace_back(mlir::omp::DeclareTargetCaptureClause::to,
+                                     owningProc->getSubprogramSymbol());
+      }
     }
 
     ClauseProcessor cp(converter, semaCtx, clauses);

flang/test/Lower/OpenMP/declare-target-interface.f90

@@ -0,0 +1,11 @@
+!RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s
+!RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-is-device %s -o - | FileCheck %s
+
+!CHECK: module attributes
+module iface
+interface
+  subroutine a()
+  !$omp declare target
+  end subroutine
+end interface
+end module