Make ClassPathEntry.sourceJar null by default

Author: fwcd

shared/src/main/kotlin/org/javacs/kt/classpath/ClassPathEntry.kt

@@ -2,4 +2,7 @@ package org.javacs.kt.classpath
 
 import java.nio.file.Path
 
-data class ClassPathEntry(val compiledJar: Path, val sourceJar: Path?)
+data class ClassPathEntry(
+    val compiledJar: Path,
+    val sourceJar: Path? = null
+)