Assign default number version (without patch version)

So that you can still build and use fzf even when the precise version
number is not injected via -ldflags.

main.go

@@ -5,13 +5,10 @@ import (
 	"github.com/junegunn/fzf/src/protector"
 )
 
-var version string
-var revision string
+var version string = "0.24"
+var revision string = "devel"
 
 func main() {
-	if len(version) == 0 {
-		panic("Invalid build: version information missing")
-	}
 	protector.Protect()
 	fzf.Run(fzf.ParseOptions(), version, revision)
 }