Fix two exceptions in "Convert concatenation to template

So #KT-23045 Fixed
So #KT-23045 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToStringTemplateIntention.kt

@@ -87,13 +87,12 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
                     val type = bindingContext.getType(expression)!!
 
                     if (KotlinBuiltIns.isChar(type)) {
-                        val value = expressionText.removePrefix("'").removeSuffix("'")
-                        return when (value) { // escape double quote and unescape single one and $
-                            "\"" -> "\\\""
-                            "\\'" -> "'"
-                            "$" -> if (forceBraces) "\\$" else "$"
-                            else -> value
-                        }
+                        return expressionText
+                            .removePrefix("'")
+                            .removeSuffix("'")
+                            .replace("\"", "\\\"")
+                            .replace("\\'", "'")
+                            .run { if (forceBraces) replace("$", "\\$") else this }
                     }
 
                     val constant = ConstantExpressionEvaluator.getConstant(expression, bindingContext)

idea/testData/intentions/convertToStringTemplate/invalidChar.kt

@@ -0,0 +1,2 @@
+// DISABLE-ERRORS
+val foo = "foo" + ' "' + "bar" + ' ""'<caret>

idea/testData/intentions/convertToStringTemplate/invalidChar.kt.after

@@ -0,0 +1,2 @@
+// DISABLE-ERRORS
+val foo = "foo \"bar \"\""<caret>

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -6858,6 +6858,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("invalidChar.kt")
+        public void testInvalidChar() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/invalidChar.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt11295.kt")
         public void testKt11295() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/kt11295.kt");