plugins BUGFIX handle empty revision correctly

Fixes #1451

Author: michalvasko

src/plugins.c

@@ -457,9 +457,8 @@ ext_get_plugin(const char *name, const char *module, const char *revision)
     assert(module);
 
     for (u = 0; u < ext_plugins_count; u++) {
-        if (!strcmp(name, ext_plugins[u].name) &&
-                !strcmp(module, ext_plugins[u].module) &&
-                (!ext_plugins[u].revision || !strcmp(revision, ext_plugins[u].revision))) {
+        if (!strcmp(name, ext_plugins[u].name) && !strcmp(module, ext_plugins[u].module) &&
+                ((!revision && !ext_plugins[u].revision) || (revision && !strcmp(revision, ext_plugins[u].revision)))) {
             /* we have the match */
             return ext_plugins[u].plugin;
         }