Various fixes detected using PVS-Studio static analyzer.

- Add FIXME tags comments to some unfixed potential bugs
- Remove some checks (always false: unsigned never < 0)
- Fix some if statements based on reviews.
- Bunch of missing `else` statements

modules/gdscript/gd_function.cpp

@@ -725,7 +725,7 @@ Variant GDFunction::call(GDInstance *p_instance, const Variant **p_args, int p_a
 								err.argument-=1;
 							}
 						}
-					} if (methodstr=="free") {
+					} else if (methodstr=="free") {
 
 						if (err.error==Variant::CallError::CALL_ERROR_INVALID_METHOD) {
 

modules/regex/regex.cpp

@@ -321,7 +321,7 @@ struct RegExNodeClass : public RegExNode {
 			case Type_lower:
 				return ('a' <= c && c <= 'z');
 			case Type_print:
-				return (0x1F < c && c < 0x1F);
+				return (0x20 < c && c < 0x7f);
 			case Type_punct:
 				return (REGEX_NODE_PUNCT.find(c) >= 0);
 			case Type_space:

modules/visual_script/visual_script_builtin_funcs.cpp

@@ -329,7 +329,7 @@ PropertyInfo VisualScriptBuiltinFunc::get_input_value_port_info(int p_idx) const
 		case LOGIC_CLAMP: {
 			if (p_idx==0)
 				return PropertyInfo(Variant::REAL,"a");
-			else if (p_idx==0)
+			else if (p_idx==0)	// is it ok to test p_idx == 0 twice?
 				return PropertyInfo(Variant::REAL,"min");
 			else
 				return PropertyInfo(Variant::REAL,"max");