Fixed crash with "register" function in plugin scripts (bug #16701)

src/plugins/scripts/lua/weechat-lua.c

@@ -149,6 +149,8 @@ weechat_lua_register (lua_State *L)
     
     /* make gcc happy */
     (void) L;
+
+    lua_current_script = NULL;
     
     name = NULL;
     version = NULL;

src/plugins/scripts/perl/weechat-perl.c

@@ -247,6 +247,8 @@ static XS (XS_weechat_register)
     /* make gcc happy */
     (void) items;
     (void) cv;
+
+    perl_current_script = NULL;
     
     if (items != 4)
     {

src/plugins/scripts/python/weechat-python.c

@@ -172,6 +172,8 @@ weechat_python_register (PyObject *self, PyObject *args)
     
     /* make gcc happy */
     (void) self;
+
+    python_current_script = NULL;
     
     name = NULL;
     version = NULL;

src/plugins/scripts/ruby/weechat-ruby.c

@@ -224,6 +224,8 @@ weechat_ruby_register (VALUE class, VALUE name, VALUE version,
     
     /* make gcc happy */
     (void) class;
+
+    ruby_current_script = NULL;
     
     if (NIL_P (name) || NIL_P (version) || NIL_P (shutdown_func) || NIL_P (description))
     {