zypp: Fix package installation using undefined data

Code introduced by commit c45e0f2 is strange.
Depending partly on uninitialized array values when an array
is not even needed, and also using the values both as enum
and as some kind of existence check.

backends/zypp/pk-backend-zypp.cpp

@@ -2746,7 +2746,6 @@ backend_install_packages_thread (PkBackendJob *job, GVariant *params, gpointer u
 		PoolStatusSaver saver;
 		pk_backend_job_set_percentage (job, 10);
 		vector<PoolItem> items;
-		VersionRelation relations[g_strv_length (package_ids)];
 		guint to_install = 0;
 
 		for (guint i = 0; package_ids[i]; i++) {
@@ -2776,43 +2775,45 @@ backend_install_packages_thread (PkBackendJob *job, GVariant *params, gpointer u
 				}
 			}
 
+			VersionRelation relation = NEWER_VERSION;
+
 			for (guint j = 0; j < installed.size (); j++) {
 				inst_pkg = &installed.at (j);
 				ret = inst_pkg->edition ().compare (Edition (split[PK_PACKAGE_ID_VERSION]));
 
-				if (relations[i] == 0 && ret < 0) {
-					relations[i] = NEWER_VERSION;
-				} else if (relations[i] != EQUAL_VERSION && ret > 0) {
-					relations[i] = OLDER_VERSION;
+				if (ret < 0) {
+					relation = NEWER_VERSION;
+				} else if (relation != EQUAL_VERSION && ret > 0) {
+					relation = OLDER_VERSION;
 					if (!latest_pkg ||
 					    latest_pkg->edition ().compare (inst_pkg->edition ()) < 0) {
 						latest_pkg = inst_pkg;
 					}
 				} else if (ret == 0) {
-					relations[i] = EQUAL_VERSION;
+					relation = EQUAL_VERSION;
 					break;
 				}
 			}
 
-			if (relations[i] == EQUAL_VERSION &&
+			if (relation == EQUAL_VERSION &&
 			    !pk_bitfield_contain (transaction_flags,
 						  PK_TRANSACTION_FLAG_ENUM_ALLOW_REINSTALL)) {
 				continue;
 			}
 
-			if (relations[i] == OLDER_VERSION &&
+			if (relation == OLDER_VERSION &&
 			    !pk_bitfield_contain (transaction_flags,
 						  PK_TRANSACTION_FLAG_ENUM_ALLOW_DOWNGRADE)) {
 				pk_backend_job_error_code (job,
 							   PK_ERROR_ENUM_PACKAGE_ALREADY_INSTALLED,
 							   "higher version \"%s\" of package %s.%s is already installed",
-							   latest_pkg->edition ().version ().c_str (),
+							   latest_pkg ? latest_pkg->edition ().version ().c_str () : "<NULL>",
 							   split[PK_PACKAGE_ID_NAME],
 							   split[PK_PACKAGE_ID_ARCH]);
 				return;
 			}
 
-			if (relations[i] && relations[i] != EQUAL_VERSION &&
+			if (relation != EQUAL_VERSION && installed.size() > 0 &&
 			    pk_bitfield_contain (transaction_flags,
 						 PK_TRANSACTION_FLAG_ENUM_JUST_REINSTALL)) {
 				pk_backend_job_error_code (job,