Corrected parser: incomplete code should never cause brace disbalance

Fixed KT-7539 fq name inserted when completing nested traits name

 #KT-7539

idea/idea-completion/testData/handlers/basic/InterfaceNameBeforeRunBug.kt.after

@@ -0,0 +1,12 @@
+package a.b.c.d
+
+class B {
+    public val mark: Mark<caret> = run {
+
+    }
+
+    interface Mark {
+    }
+}
+
+// ELEMENT: Mark