Simplication and optimization of error message handling.

FossilOrigin-Name: 9d347f547e7ba9590b0c68edf50a14ad94a2bb92
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 1f10c31..8e1436e 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3157,6 +3157,7 @@
 int sqlite3ValueBytes(sqlite3_value*, u8);
 void sqlite3ValueSetStr(sqlite3_value*, int, const void *,u8, 
                         void(*)(void*));
+void sqlite3ValueSetNull(sqlite3_value*);
 void sqlite3ValueFree(sqlite3_value*);
 sqlite3_value *sqlite3ValueNew(sqlite3 *);
 char *sqlite3Utf16to8(sqlite3 *, const void*, int, u8);