Update source-solver to address possible NPE with non-existent class references in AST

Author: Col-E

gradle/libs.versions.toml

@@ -42,7 +42,7 @@ regex = "0.1.19"
 richtextfx = "cbdcbd1440"
 treemapfx = "1.1.0"
 vineflower = "1.11.1"
-sourcesolver = "1.1.5"
+sourcesolver = "1.1.6"
 # Plugins
 benmanes-versions = "0.52.0"
 gradle-coverage-report-aggregator = "1.3.2"