[FE] Fix exception from the 'UnusedChecker' on a destructuring

^KT-55973 Fixed

analysis/analysis-api-fe10/tests-gen/org/jetbrains/kotlin/analysis/api/fe10/test/cases/generated/cases/components/diagnosticProvider/Fe10IdeNormalAnalysisSourceModuleCollectDiagnosticsTestGenerated.java

@@ -69,4 +69,10 @@ public class Fe10IdeNormalAnalysisSourceModuleCollectDiagnosticsTestGenerated ex
     public void testUnresolved() throws Exception {
         runTest("analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unresolved.kt");
     }
+
+    @Test
+    @TestMetadata("unusedDestructuring.kt")
+    public void testUnusedDestructuring() throws Exception {
+        runTest("analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unusedDestructuring.kt");
+    }
 }

analysis/analysis-api-fir/tests-gen/org/jetbrains/kotlin/analysis/api/fir/test/cases/generated/cases/components/diagnosticProvider/FirIdeNormalAnalysisSourceModuleCollectDiagnosticsTestGenerated.java

@@ -69,4 +69,10 @@ public class FirIdeNormalAnalysisSourceModuleCollectDiagnosticsTestGenerated ext
     public void testUnresolved() throws Exception {
         runTest("analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unresolved.kt");
     }
+
+    @Test
+    @TestMetadata("unusedDestructuring.kt")
+    public void testUnusedDestructuring() throws Exception {
+        runTest("analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unusedDestructuring.kt");
+    }
 }

analysis/analysis-api-standalone/tests-gen/org/jetbrains/kotlin/analysis/api/standalone/fir/test/cases/generated/cases/components/diagnosticProvider/FirStandaloneNormalAnalysisSourceModuleCollectDiagnosticsTestGenerated.java

@@ -69,4 +69,10 @@ public class FirStandaloneNormalAnalysisSourceModuleCollectDiagnosticsTestGenera
     public void testUnresolved() throws Exception {
         runTest("analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unresolved.kt");
     }
+
+    @Test
+    @TestMetadata("unusedDestructuring.kt")
+    public void testUnusedDestructuring() throws Exception {
+        runTest("analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unusedDestructuring.kt");
+    }
 }

analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unusedDestructuring.kt

@@ -0,0 +1,11 @@
+class Test {
+    private fun test(x: Int, y: Int) {
+        val (_, _) = invert(x, y)
+    }
+
+    private fun invert(x: Int, y: Int): Point {
+        return Point(-x, -y)
+    }
+}
+
+data class Point(val x: Int, val y: Int)

analysis/analysis-api/testData/components/diagnosticsProvider/diagnostics/unusedDestructuring.txt

@@ -0,0 +1 @@
+Diagnostics from elements:

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/UnusedChecker.kt

@@ -79,7 +79,12 @@ object UnusedChecker : AbstractFirPropertyInitializationChecker() {
                 variableSymbol.lazyResolveToPhase(FirResolvePhase.BODY_RESOLVE)
                 @OptIn(SymbolInternals::class)
                 val variable = variableSymbol.fir
-                val variableSource = variable.source.takeIf { it?.elementType != KtNodeTypes.DESTRUCTURING_DECLARATION }
+                val variableSource = variable.source
+
+                if (variableSource?.elementType == KtNodeTypes.DESTRUCTURING_DECLARATION) {
+                    continue
+                }
+
                 when {
                     data == VariableStatus.UNUSED -> {
                         when {