[ADD] Option to silent empty log

	SetNoEmpty(true)

README.md

@@ -200,6 +200,13 @@ log.SetExitOnError(true) // Exit if log level reach Error or worst.
 ```
 If the case, the error message is generated and a debug level may appear, depending current verbosity, indicating that an immediate exit occured, and telling what is the program exit code. The exit code is equal to the level reached by the last fatal error, i.e 1 (emergency) to 4 (error) , or even 5 if warning considered error.
 
+Set option to silent empty log messages :
+
+```go
+slogan.SetNoEmpty(true) // Silent empty messages
+```
+Note: Exit on error is done even if message is empty and option set.
+
 ### Formats ###
 
 Formats can be configured by settings new "Sprintf" values to the three arguments passed to `slogan` functions :

go.mod

@@ -1,3 +1,8 @@
 module github.com/crownedgrouse/slogan
 
 go 1.12
+
+require (
+	github.com/bclicn/color v0.0.0-20180711051946-108f2023dc84
+	golang.org/x/crypto v0.9.0
+)

slogan.go

@@ -128,6 +128,8 @@ var CallerBase bool = true
 var Colorize bool = true
 // should colorize even if output is not a terminal ?
 var ForceColorize bool = false 
+// should empty log string logged ?
+var NoEmpty bool = false
 
 //************ Exported functions for configuration *************
 
@@ -161,6 +163,11 @@ func SetForceColor(mode bool) {
 	ForceColorize = mode
 }
 
+/**/
+func SetNoEmpty(mode bool) {
+	NoEmpty = mode
+}
+
 /* Get color map */
 func GetColors() map[int]string {
 	return colors
@@ -390,8 +397,14 @@ func decr_offset() {
 // 1st argument is level integer, 2nd argument log string
 func Log(level int, log string) {
 	if Verbosity >= level {
-		Str := logfmt(level, log)
-		logger.Println(Str)
+		allow := true
+		if NoEmpty == true && len(log) == 0 {
+			allow = false
+		}
+		if allow {
+			Str := logfmt(level, log)
+			logger.Println(Str)
+		}
 	}
 	if ((level < Lwarning) || (level == Lwarning && WarningAsError == true)) && (ExitOnError == true) {
 		incr_offset()