More descriptive error message

When the file's not found, say so, rather than falling through and failing with "Cannot DIM negative amount".

Version 0.73. Tagged as 'ABRelease-0_73'

VersionNum

-/* (0.72)
+/* (0.73)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        0.72
+#define Module_MajorVersion_CMHG        0.73
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                01 Feb 2016
+#define Module_Date_CMHG                29 Mar 2016
 
-#define Module_MajorVersion             "0.72"
-#define Module_Version                  72
+#define Module_MajorVersion             "0.73"
+#define Module_Version                  73
 #define Module_MinorVersion             ""
-#define Module_Date                     "01 Feb 2016"
+#define Module_Date                     "29 Mar 2016"
 
-#define Module_ApplicationDate          "01-Feb-16"
+#define Module_ApplicationDate          "29-Mar-16"
 
 #define Module_ComponentName            "ABRelease"
 #define Module_ComponentPath            "castle/RiscOS/Utilities/Autobuild/ABRelease"
 
-#define Module_FullVersion              "0.72"
-#define Module_HelpVersion              "0.72 (01 Feb 2016)"
-#define Module_LibraryVersionInfo       "0:72"
+#define Module_FullVersion              "0.73"
+#define Module_HelpVersion              "0.73 (29 Mar 2016)"
+#define Module_LibraryVersionInfo       "0:73"