Fix for null pointer dereference

When there are no items in the scroll list, the check of select/adjust clicks were using event_item=0 and looking up in a NULL sdata list.
Move the (existing) early exit a bit higher up, since there are no entries in the list the _select_item() calls aren't needed anyway.
Fixes issue reported by John Rickman https://www.riscosopen.org/forum/forums/4/topics/4011

Version 0.41. Tagged as 'Gadgets-0_41'

VersionNum

-/* (0.40)
+/* (0.41)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        0.40
+#define Module_MajorVersion_CMHG        0.41
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                28 Nov 2015
+#define Module_Date_CMHG                25 Mar 2016
 
-#define Module_MajorVersion             "0.40"
-#define Module_Version                  40
+#define Module_MajorVersion             "0.41"
+#define Module_Version                  41
 #define Module_MinorVersion             ""
-#define Module_Date                     "28 Nov 2015"
+#define Module_Date                     "25 Mar 2016"
 
-#define Module_ApplicationDate          "28-Nov-15"
+#define Module_ApplicationDate          "25-Mar-16"
 
 #define Module_ComponentName            "Gadgets"
 #define Module_ComponentPath            "castle/RiscOS/Sources/Toolbox/Gadgets"
 
-#define Module_FullVersion              "0.40"
-#define Module_HelpVersion              "0.40 (28 Nov 2015)"
-#define Module_LibraryVersionInfo       "0:40"
+#define Module_FullVersion              "0.41"
+#define Module_HelpVersion              "0.41 (25 Mar 2016)"
+#define Module_LibraryVersionInfo       "0:41"

c/ScrollList

@@ -1456,6 +1456,10 @@ static _kernel_oserror *scrolllist_mclick(const PrivateScrollList *sdata,
 
     event_item = -mouse_y / item_height;
 
+    /* SNB: 19980518: changed condition to >= to stop "extra item" events. */
+    if (event_item >= sdata->no_entries)
+        return NULL;
+
     if (click->buttons >= 256)
     {
         if ((click->buttons / 256) & (1<<0))
@@ -1470,11 +1474,6 @@ static _kernel_oserror *scrolllist_mclick(const PrivateScrollList *sdata,
     }
 
     // Send event -
-    /* SNB: 19980518: changed condition to >= to stop "extra item" events. */
-
-    if (event_item >= sdata->no_entries)
-        return NULL;
-
     event_flags = 0;
 
     if (click->buttons < 16)