Fix pkg-build crash on system package drop

2 files changed, 24 insertions, 5 deletions

diff --git a/bpkg/pkg-build.cxx b/bpkg/pkg-build.cxx
index 80e14f0..27e509b 100644
--- a/bpkg/pkg-build.cxx
+++ b/bpkg/pkg-build.cxx
@@ -4260,13 +4260,20 @@ namespace bpkg
       {
         if (*p.action == build_package::drop)
         {
-          transaction t (db, !simulate /* start */);
-          pkg_purge (c, t, sp, simulate); // Commits the transaction.
+          // Note that the selected system package has already gone being
+          // disfigured (see above).
+          //
+          if (sp != nullptr)
+          {
+            transaction t (db, !simulate /* start */);
+            pkg_purge (c, t, sp, simulate); // Commits the transaction.
 
-          if (verbose && !o.no_result ())
-            text << "purged " << *sp;
+            if (verbose && !o.no_result ())
+              text << "purged " << *sp;
+
+            sp = nullptr;
+          }
 
-          sp = nullptr;
           break;
         }
 
diff --git a/tests/pkg-system.testscript b/tests/pkg-system.testscript
index e8ad676..678e838 100644
--- a/tests/pkg-system.testscript
+++ b/tests/pkg-system.testscript
@@ -908,4 +908,16 @@ rep_remove += -d cfg 2>!
 
     $pkg_drop foo
   }
+
+  : unhold
+  :
+  : Test that the system package get purged being unhold.
+  :
+  {
+    $clone_cfg;
+
+    $pkg_build 'sys:foo' 2>'configured sys:foo/*';
+
+    $pkg_build ?foo 2>'purged foo/*'
+  }
 }