Panic when fzf was built without version information

So that the package maintainers would immediately know that the build is
incorrect. But is there a way to make build simply fail?

Related: junegunn/fzf.vim#1150

BUILD.md

@@ -17,20 +17,11 @@ make
 # Build fzf binary and copy it to bin directory
 make install
 
-# Build 32-bit and 64-bit executables and tarballs in target
-make release
-
-# Make release archives for all supported platforms in target
-make release-all
-```
-
-### Using `go get`
+# Build fzf binaries and archives for all platforms using goreleaser
+make build
 
-Alternatively, you can build fzf directly with `go get` command without
-manually cloning the repository.
-
-```sh
-go get -u github.com/junegunn/fzf
+# Publish GitHub release
+make release
 ```
 
 Third-party libraries used

main.go

@@ -9,6 +9,9 @@ var version string
 var revision string
 
 func main() {
+	if len(version) == 0 {
+		panic("Invalid build: version information missing")
+	}
 	protector.Protect()
 	fzf.Run(fzf.ParseOptions(), version, revision)
 }