Fixed some obvious typos in error messages

In some errors, there were closing quotation marks but no opening (e. g. "Unable to iterate on object of type  " + 
Variant::get_type_name(container->get_type()) + "'."

modules/gdscript/gdscript_function.cpp

@@ -1419,7 +1419,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 				if (!container->iter_init(*counter, valid)) {
 #ifdef DEBUG_ENABLED
 					if (!valid) {
-						err_text = "Unable to iterate on object of type  " + Variant::get_type_name(container->get_type()) + "'.";
+						err_text = "Unable to iterate on object of type '" + Variant::get_type_name(container->get_type()) + "'.";
 						OPCODE_BREAK;
 					}
 #endif
@@ -1432,7 +1432,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 					*iterator = container->iter_get(*counter, valid);
 #ifdef DEBUG_ENABLED
 					if (!valid) {
-						err_text = "Unable to obtain iterator object of type  " + Variant::get_type_name(container->get_type()) + "'.";
+						err_text = "Unable to obtain iterator object of type '" + Variant::get_type_name(container->get_type()) + "'.";
 						OPCODE_BREAK;
 					}
 #endif
@@ -1452,7 +1452,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 				if (!container->iter_next(*counter, valid)) {
 #ifdef DEBUG_ENABLED
 					if (!valid) {
-						err_text = "Unable to iterate on object of type  " + Variant::get_type_name(container->get_type()) + "' (type changed since first iteration?).";
+						err_text = "Unable to iterate on object of type '" + Variant::get_type_name(container->get_type()) + "' (type changed since first iteration?).";
 						OPCODE_BREAK;
 					}
 #endif
@@ -1465,7 +1465,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 					*iterator = container->iter_get(*counter, valid);
 #ifdef DEBUG_ENABLED
 					if (!valid) {
-						err_text = "Unable to obtain iterator object of type  " + Variant::get_type_name(container->get_type()) + "' (but was obtained on first iteration?).";
+						err_text = "Unable to obtain iterator object of type '" + Variant::get_type_name(container->get_type()) + "' (but was obtained on first iteration?).";
 						OPCODE_BREAK;
 					}
 #endif