Fixed the main function signature

src/org/jetbrains/jet/j2k/Converter.kt

@@ -770,7 +770,7 @@ public fun createMainFunction(file: PsiFile): String {
 
     if (classNamesWithMains.size() > 0) {
         var className: String? = classNamesWithMains.get(0)?.getFirst()
-        return MessageFormat.format("fun main(args : Array<String?>?) = {0}.main(args)", className)!!
+        return MessageFormat.format("fun main(args : Array<String>) = {0}.main(args as Array<String?>?)", className)!!
     }
 
     return ""

tests/testData/ast/issues/file/kt-638.kt

@@ -35,4 +35,4 @@ var i3 : Identifier<Any?>? = Identifier.init<String?>("name")
 }
 }
 }
-fun main(args : Array<String?>?) = User.main(args)
+fun main(args : Array<String>) = User.main(args as Array<String?>?)

tests/testData/ast/issues/file/kt-871.kt

@@ -6,4 +6,4 @@ System.out?.println("Halo!")
 }
 }
 }
-fun main(args : Array<String?>?) = Program.main(args)
+fun main(args : Array<String>) = Program.main(args as Array<String?>?)

tests/testData/ast/switch/file/comlicatedFallDown.kt

@@ -85,4 +85,4 @@ for (i in 1..12) test(i)
 }
 }
 }
-fun main(args : Array<String?>?) = SwitchDemo.main(args)
+fun main(args : Array<String>) = SwitchDemo.main(args as Array<String?>?)

tests/testData/ast/switch/file/fallDown.kt

@@ -16,4 +16,4 @@ System.out?.println(monthString)
 }
 }
 }
-fun main(args : Array<String?>?) = SwitchDemo.main(args)
+fun main(args : Array<String>) = SwitchDemo.main(args as Array<String?>?)

tests/testData/ast/switch/file/kt-539.kt

@@ -49,4 +49,4 @@ System.out?.println(monthString)
 }
 }
 }
-fun main(args : Array<String?>?) = SwitchDemo.main(args)
+fun main(args : Array<String>) = SwitchDemo.main(args as Array<String?>?)