string internal set method has additional safeguard for bad data

include/blah/graphics/batch.h

@@ -199,6 +199,8 @@ namespace Blah
 			u8 wash;
 			u8 fill;
 			u8 pad;
+
+			Vertex() = default;
 		};
 
 		struct DrawBatch

src/containers/str.cpp

@@ -471,12 +471,22 @@ void Str::set(const char* start, const char* end)
 	if (end == nullptr)
 		end = start + strlen(start);
 
+	// make sure it actually contains characters
+	int len = (int)(end - start);
+	if (len <= 0)
+	{
+		clear();
+	}
+	else
+	{
+		m_length = len;
+		
 		// reserve
-	m_length = (int)(end - start);
 		reserve(m_length);
 
 		// copy the data over
 		char* ptr = data();
 		memcpy(ptr, start, m_length);
 		ptr[m_length] = '\0';
+	}
 }