NPE in BlockStructureBraces

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/rules/BlockStructureBraces.kt

@@ -178,7 +178,9 @@ class BlockStructureBraces(private val configRules: List<RulesConfig>) : Rule("b
                 if (braceSpace == null || braceSpace.elementType != WHITE_SPACE) {
                     node.addChild(PsiWhiteSpaceImpl(" "), nodeBefore)
                 } else {
-                    (braceSpace as LeafPsiElement).replaceWithText(" ")
+                    val spaceParent = braceSpace.treeParent
+                    spaceParent.addChild(PsiWhiteSpaceImpl(" "), braceSpace)
+                    spaceParent.removeChild(braceSpace)
                 }
             }
         }

diktat-rules/src/test/resources/test/smoke/src/main/kotlin/Example3Expected.kt

@@ -21,3 +21,13 @@ fun mains() {
     httpClient.doRequest()
 }
 
+class Example {
+    fun foo() {
+        if (condition1) {
+            if (condition2) {
+                bar()
+            }
+        }
+    }
+}
+

diktat-rules/src/test/resources/test/smoke/src/main/kotlin/Example3Test.kt

@@ -21,4 +21,12 @@ fun mains() {
                 timeout = 100
             }
     httpClient.doRequest()
-}
+}
+
+class Example {
+    fun foo() {
+        if (condition1)
+            if (condition2)
+                bar()
+    }
+}