fix compiler crash when taking address of label

compiler/src/prog8/compiler/target/cpu6502/codegen/AsmGen.kt

@@ -493,8 +493,11 @@ internal class AsmGen(private val program: Program,
         return newName
     }
 
-    internal fun asmSymbolName(identifier: IdentifierReference) =
-        fixNameSymbols(identifier.nameInSource.joinToString("."))
+    internal fun asmSymbolName(identifier: IdentifierReference): String {
+        val target = identifier.targetStatement(program)
+        val prefix = if(target is Label) "_" else ""
+        return fixNameSymbols(prefix+identifier.nameInSource.joinToString("."))
+    }
 
     internal fun asmSymbolName(regs: RegisterOrPair): String =
         if (regs in Cx16VirtualRegisters)
@@ -1264,14 +1267,7 @@ $label              nop""")
         val label = jump.generatedLabel
         val addr = jump.address
         return when {
-            ident!=null -> {
-                val target = ident.targetStatement(program)
-                val asmName = asmSymbolName(ident)
-                if(target is Label)
-                    "_$asmName"  // prefix with underscore to jump to local label
-                else
-                    asmName
-            }
+            ident!=null -> asmSymbolName(ident)
             label!=null -> label
             addr!=null -> addr.toHex()
             else -> "????"

compiler/src/prog8/compiler/target/cpu6502/codegen/assignment/AssignmentAsmGen.kt

@@ -145,7 +145,7 @@ internal class AssignmentAsmGen(private val program: Program, private val asmgen
             SourceStorageKind.EXPRESSION -> {
                 when(val value = assign.source.expression!!) {
                     is AddressOf -> {
-                        val sourceName = asmgen.asmVariableName(value.identifier)
+                        val sourceName = asmgen.asmSymbolName(value.identifier)
                         assignAddressOf(assign.target, sourceName)
                     }
                     is NumericLiteralValue -> throw AssemblyError("source kind should have been literalnumber")

compiler/src/prog8/optimizer/StatementOptimizer.kt

@@ -59,8 +59,7 @@ internal class StatementOptimizer(private val program: Program,
 
                 // TODO: only do this optimization if the arg is a known-constant string literal instead of a user defined variable. We can't see the difference here yet.
 
-                val vardecl = stringVar.targetVarDecl(program)!!
-                val string = vardecl.value as? StringLiteralValue
+                val string = stringVar.targetVarDecl(program)?.value as? StringLiteralValue
                 if(string!=null) {
                     val pos = functionCallStatement.position
                     if (string.value.length == 1) {