fix mavenCentralPublish.gradle version determination

Author: johanneshiry

gradle/scripts/mavenCentralPublish.gradle

@@ -12,10 +12,10 @@ task javadocJar(type: Jar, dependsOn: javadoc) {
 if (project.hasProperty('user') && project.hasProperty('password')) {
 
 	// snapshot version differs from normal version
-	def version = project.hasProperty('snapshot') ? "${semver.major}.${semver.minor}-SNAPSHOT" : this.version
+	String versionString = project.hasProperty('snapshot') ? "${semver.major}.${semver.minor}-SNAPSHOT" : this.version.toString()
 
 	signing {
-		required { !version.endsWith('SNAPSHOT') }
+		required { !versionString.endsWith('SNAPSHOT') }
 		if (required)
 			sign(publishing.publications)
 	}
@@ -80,7 +80,7 @@ if (project.hasProperty('user') && project.hasProperty('password')) {
 				removeTestDependenciesFromPom(pom)
 				groupId group
 				artifactId 'PowerSystemDataModel'
-				version version
+				version versionString
 
 				from components.java
 				artifact sourcesJar
@@ -92,7 +92,7 @@ if (project.hasProperty('user') && project.hasProperty('password')) {
 			maven {
 				def releasesRepoUrl = "https://oss.sonatype.org/service/local/staging/deploy/maven2/"
 				def snapshotsRepoUrl = "https://oss.sonatype.org/content/repositories/snapshots/"
-				url = version.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl
+				url = versionString.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl
 				credentials {
 					username project.getProperty('user')
 					password project.getProperty('password')