Fix crash in go_symbol_package_name

go_symbol_package_name package name asserts that it is only passed a
Go symbol, but this is not enforced by one caller.  It seems simplest
to just check and return early in this case.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=17876
Reviewed-By: Andrew Burgess <aburgess@redhat.com>

gdb/testsuite/gdb.go/no-package.exp

@@ -0,0 +1,31 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2023 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Regression test for a crash in go_symbol_package_name.
+
+load_lib "go.exp"
+
+require allow_go_tests support_go_compile !use_gdb_stub
+
+standard_testfile integers.go
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} {debug go}]} {
+    return -1
+}
+
+# The bug was that stopping in _start would crash.
+runto "*_start" message