Fixed this call in primitive expansions

Who would've thought that a 'this' can be a non-object :thinking-face:

JavaBytecodeCompiler/src/main/java/org/openzen/zenscript/javabytecode/compiler/JavaExpressionVisitor.java

 
 	@Override
 	public Void visitThis(ThisExpression expression) {
-		javaWriter.loadObject(0);
+		javaWriter.load(context.getType(expression.type), 0);
 		return null;
 	}