Fix compiler warnings on x86 Linux
diff --git a/src/x86/Gos-linux.c b/src/x86/Gos-linux.c
index 255696c..31f83ba 100644
--- a/src/x86/Gos-linux.c
+++ b/src/x86/Gos-linux.c
@@ -153,6 +153,9 @@
     case X86_SCF_LINUX_RT_SIGFRAME:
       addr += LINUX_UC_MCONTEXT_OFF;
       break;
+
+    default:
+      return DWARF_NULL_LOC;
     }
 
   switch (reg)