Fix for bad error pointer deleting non existent sprite

Doing *WimpKillSprite _not_there_  had the following behaviour

Priority   | Sprite exists  Sprite doesn't  Sprite is ROM
Lo then Hi | Deletes        Bad error ptr   Silence
Hi then Lo | Deletes        Silence         Silence

The bad error pointer was caused by an early return if the high priority pool is the ROM sprites (because the earlier failure to find it in the low priority pools set V, and the early return used TEQ, so the error pointer in R0 was the SpriteOp reason code).
Proceed to try to look up the sprite, even if there's no hope of deleting it, in order to get a valid error message.

Version 5.61. Tagged as 'Wimp-5_61'

VersionASM

@@ -11,13 +11,13 @@
                         GBLS    Module_HelpVersion
                         GBLS    Module_ComponentName
                         GBLS    Module_ComponentPath
-Module_MajorVersion     SETS    "5.60"
-Module_Version          SETA    560
+Module_MajorVersion     SETS    "5.61"
+Module_Version          SETA    561
 Module_MinorVersion     SETS    ""
-Module_Date             SETS    "17 Feb 2018"
-Module_ApplicationDate  SETS    "17-Feb-18"
+Module_Date             SETS    "18 Mar 2018"
+Module_ApplicationDate  SETS    "18-Mar-18"
 Module_ComponentName    SETS    "Wimp"
 Module_ComponentPath    SETS    "castle/RiscOS/Sources/Desktop/Wimp"
-Module_FullVersion      SETS    "5.60"
-Module_HelpVersion      SETS    "5.60 (17 Feb 2018)"
+Module_FullVersion      SETS    "5.61"
+Module_HelpVersion      SETS    "5.61 (18 Mar 2018)"
                         END

VersionNum

-/* (5.60)
+/* (5.61)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        5.60
+#define Module_MajorVersion_CMHG        5.61
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                17 Feb 2018
+#define Module_Date_CMHG                18 Mar 2018
 
-#define Module_MajorVersion             "5.60"
-#define Module_Version                  560
+#define Module_MajorVersion             "5.61"
+#define Module_Version                  561
 #define Module_MinorVersion             ""
-#define Module_Date                     "17 Feb 2018"
+#define Module_Date                     "18 Mar 2018"
 
-#define Module_ApplicationDate          "17-Feb-18"
+#define Module_ApplicationDate          "18-Mar-18"
 
 #define Module_ComponentName            "Wimp"
 #define Module_ComponentPath            "castle/RiscOS/Sources/Desktop/Wimp"
 
-#define Module_FullVersion              "5.60"
-#define Module_HelpVersion              "5.60 (17 Feb 2018)"
-#define Module_LibraryVersionInfo       "5:60"
+#define Module_FullVersion              "5.61"
+#define Module_HelpVersion              "5.61 (18 Mar 2018)"
+#define Module_LibraryVersionInfo       "5:61"

s/Wimp04

@@ -4097,7 +4097,8 @@ do_spriteop
         TEQ     R14, #SpriteReason_DeleteSprite ; is able to get here, provided it came via *WimpKillSprite
         LDREQ   R14, baseofromsprites
         TEQEQ   R1, R14
-        Pull    "PC", EQ                        ; don't attempt to delete ROM sprites!
+        ASSERT  (SpriteReason_SelectSprite :OR: 1) = SpriteReason_DeleteSprite
+        BICEQ   R0, R0, #1              ; don't attempt to delete ROM sprites, but do get an error if it's not there
       ]
         LDR     R14,lengthflags
         CMP     R14,#0                  ; if length 0, then R2 --> sprite