NPE in BlockStructureBraces when there are two nested ifs without braces

[petertrr]

Describe the bug

class Example {
    fun foo() {
        if (condition1)
            if (condition2)
                bar()
    }
}

Expected behavior

All ifs should get surrounded with braces.

Observed behavior

java.lang.NullPointerException
    at org.jetbrains.kotlin.com.intellij.psi.impl.source.codeStyle.CodeEditUtil.saveWhitespacesInfo (CodeEditUtil.java:122)
    at org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.ChangeUtil.saveIndentationToCopy (ChangeUtil.java:106)
    at org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.ChangeUtil.copyLeafWithText (ChangeUtil.java:82)
    at org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.LeafElement.replaceWithText (LeafElement.java:154)
    at org.cqfn.diktat.ruleset.rules.BlockStructureBraces$checkOpenBraceOnSameLine$1.invoke (BlockStructureBraces.kt:181)
    at org.cqfn.diktat.ruleset.rules.BlockStructureBraces$checkOpenBraceOnSameLine$1.invoke (BlockStructureBraces.kt:53)

Environment information

• diktat version: 0.1.3
• build tool (maven/gradle): maven
• how is diktat run (CLI, plugin, etc.): plugin
• kotlin version: 1.4.10