Tolerate weird class names, as seen in functionaljava

[timtebeek]

They are using fj.data.$, which then leads to an empty String.

First noticed on recipe runs against rewrite-migrate-java, where the previous lead to:

Caused by: java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
        at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
        at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
        at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
        at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
        at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
        at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
        at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
        at org.openrewrite.java.marker.JavaSourceSet.isDeclarable(JavaSourceSet.java:333)
        at org.openrewrite.java.marker.JavaSourceSet.typesFromPath(JavaSourceSet.java:281)
        at org.openrewrite.java.marker.JavaSourceSet.build(JavaSourceSet.java:210)
        at org.openrewrite.gradle.isolated.DefaultProjectParser.parse(DefaultProjectParser.java:836)
        ... 125 more

[timtebeek]

The failure to now run the receive-pr workflow on the PR after adding functionaljava to the classpath perfectly illustrates this exact issue.