ckdb - log errors for calls to _data_to_buf with null data

src/ckdb.h

@@ -58,7 +58,7 @@
 
 #define DB_VLOCK "1"
 #define DB_VERSION "1.0.7"
-#define CKDB_VERSION DB_VERSION"-2.515"
+#define CKDB_VERSION DB_VERSION"-2.516"
 
 #define WHERE_FFL " - from %s %s() line %d"
 #define WHERE_FFL_HERE __FILE__, __func__, __LINE__

src/ckdb_data.c

@@ -505,9 +505,27 @@ void _txt_to_double(char *nam, char *fld, double *data, size_t siz, WHERE_FFL_AR
 
 char *_data_to_buf(enum data_type typ, void *data, char *buf, size_t siz, WHERE_FFL_ARGS)
 {
+	static bool had_null = false;
 	struct tm tm;
 	double d;
 
+	// Return an empty string but only log a console message the first time
+	if (!data) {
+		// locking doesn't matter - if we get extra messages
+		if (!had_null) {
+			had_null = true;
+			LOGEMERG("%s() BUG - called with null data - check"
+				 " log file" WHERE_FFL,
+				 __func__, WHERE_FFL_PASS);
+		}
+		LOGNOTICE("%s() BUG - called with null data typ=%d" WHERE_FFL,
+			  __func__, (int)typ, WHERE_FFL_PASS);
+		if (!buf)
+			buf = malloc(1);
+		*buf = '\0';
+		return buf;
+	}
+
 	if (!buf) {
 		switch (typ) {
 			case TYPE_STR: