Fix disabling JPQL support - properly turn off semantic highlighting

Author: BoykoAlex

headless-services/spring-boot-language-server/src/main/java/org/springframework/ide/vscode/boot/java/JdtSemanticTokensHandler.java

@@ -54,7 +54,7 @@ public JdtSemanticTokensHandler(CompilationUnitCache cuCache, JavaProjectFinder
 				tokenProvidersList.add(tp);
 			}
 		}
-		this.tokenProviders = tokenProviders;
+		this.tokenProviders = tokenProvidersList;
 		this.legend = new SemanticTokensLegend(
 				tokenProviders.stream().flatMap(tp -> tp.getTokenTypes().stream()).distinct().collect(Collectors.toList()),
 				tokenProviders.stream().flatMap(tp -> tp.getTokenModifiers().stream()).distinct().collect(Collectors.toList())
@@ -117,7 +117,7 @@ private List<SemanticTokenData> computeTokens(List<JdtSemanticTokensProvider> ap
 			// If there are tokens computed then also run JDT LS tokens provider not to lose JDT LS semantic highlights
 			cu.accept(jdtLsProvider.getTokensComputer(jp, cu, collector));
 		}
-		return collector.get();
+		return collector.isEmpty() ? null : collector.get();
 	}
 
 }