Fixed a bug in find_tab_char_and_size().

src/source.cc

@@ -703,7 +703,7 @@ bool Source::View::on_button_press_event(GdkEventButton *event) {
 }
 
 std::pair<char, unsigned> Source::View::find_tab_char_and_size() {
-  const std::regex indent_regex("^([ \t]+).*$");
+  const std::regex indent_regex("^([ \t]+)(.*)$");
   auto size=get_buffer()->get_line_count();
   std::unordered_map<char, size_t> tab_chars;
   std::unordered_map<unsigned, size_t> tab_sizes;
@@ -711,8 +711,17 @@ std::pair<char, unsigned> Source::View::find_tab_char_and_size() {
   for(int c=0;c<size;c++) {
     auto line=get_line(c);
     std::smatch sm;
+    std::string str;
     if(std::regex_match(line, sm, indent_regex)) {
-      auto str=sm[1].str();
+      if(sm[2].str().size()==0)
+        continue;
+      str=sm[1].str();
+    }
+    else {
+      str="";
+      if(line.size()==0)
+        continue;
+    }
     
     long tab_diff=abs(static_cast<long>(str.size()-last_tab_size));
     if(tab_diff>0) {
@@ -734,7 +743,6 @@ std::pair<char, unsigned> Source::View::find_tab_char_and_size() {
         tab_chars[str[0]]=1;
     }
   }
-  }
   char found_tab_char=0;
   size_t occurences=0;
   for(auto &tab_char: tab_chars) {