Fix null pointer dereference in stack backtrace code

Detail:
  c/armsys - _kernel_language will return NULL if the PC was outside any known library language block, so make sure to check for that before dereferencing the pointer
Admin:
  Builds, untested


Version 5.86. Tagged as 'RISC_OSLib-5_86'

VersionASM

@@ -11,13 +11,13 @@
                         GBLS    Module_HelpVersion
                         GBLS    Module_ComponentName
                         GBLS    Module_ComponentPath
-Module_MajorVersion     SETS    "5.85"
-Module_Version          SETA    585
+Module_MajorVersion     SETS    "5.86"
+Module_Version          SETA    586
 Module_MinorVersion     SETS    ""
-Module_Date             SETS    "03 Apr 2015"
-Module_ApplicationDate  SETS    "03-Apr-15"
+Module_Date             SETS    "30 Jun 2015"
+Module_ApplicationDate  SETS    "30-Jun-15"
 Module_ComponentName    SETS    "RISC_OSLib"
 Module_ComponentPath    SETS    "castle/RiscOS/Sources/Lib/RISC_OSLib"
-Module_FullVersion      SETS    "5.85"
-Module_HelpVersion      SETS    "5.85 (03 Apr 2015)"
+Module_FullVersion      SETS    "5.86"
+Module_HelpVersion      SETS    "5.86 (30 Jun 2015)"
                         END

VersionNum

-/* (5.85)
+/* (5.86)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        5.85
+#define Module_MajorVersion_CMHG        5.86
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                03 Apr 2015
+#define Module_Date_CMHG                30 Jun 2015
 
-#define Module_MajorVersion             "5.85"
-#define Module_Version                  585
+#define Module_MajorVersion             "5.86"
+#define Module_Version                  586
 #define Module_MinorVersion             ""
-#define Module_Date                     "03 Apr 2015"
+#define Module_Date                     "30 Jun 2015"
 
-#define Module_ApplicationDate          "03-Apr-15"
+#define Module_ApplicationDate          "30-Jun-15"
 
 #define Module_ComponentName            "RISC_OSLib"
 #define Module_ComponentPath            "castle/RiscOS/Sources/Lib/RISC_OSLib"
 
-#define Module_FullVersion              "5.85"
-#define Module_HelpVersion              "5.85 (03 Apr 2015)"
-#define Module_LibraryVersionInfo       "5:85"
+#define Module_FullVersion              "5.86"
+#define Module_HelpVersion              "5.86 (30 Jun 2015)"
+#define Module_LibraryVersionInfo       "5:86"

c/armsys

@@ -923,7 +923,7 @@ void _backtrace(int why, int *address, _kernel_unwindblock *uwb)
         char *name = 0;
         int *fp = (int *) uwb->fp;
         _kernel_swi_regs r;
-        if (lang[0]=='C' && lang[1]==0) {
+        if (lang && (lang[0]=='C') && (lang[1]==0)) {
             z = (int *)(fp[0] &~ psr_mask);
 /* Check that when I save pc in a STM instruction it could save PC+8 or  */
 /* PC+12 beyond the instruction.                                         */